Maísa Silva

Diet supplementation with acai (Euterpe oleracea Mart.) pulp improves biomarkers of oxidative stress and the serum lipid profile in rats.

OBJECTIVE We investigated the antioxidant potential and hypocholesterolemic effects of acai (Euterpe oleracea Mart.) pulp ingestion in rats fed a standard or hypercholesterolemic diet. METHODS Female Fischer rats were fed a standard AIN-93 M diet (control) or a hypercholesterolemic diet that contained 25% soy oil and 1% cholesterol. The test diet was supplemented with 2% acai pulp (dry wt/wt) for control (group CA) and hypercholesterolemic rats (group HA) for 6 wk. At the end of the experimental period, rats were sacrificed and the blood and livers were collected. To evaluate the effect of acai consumption, levels of protein carbonyl and sulfhydryl groups, superoxide dismutase and paraoxonase activities, and lipid profiles of the sera were measured. RESULTS Animals that were fed the hypercholesterolemic diet presented increased levels of total and non-high-density lipoprotein cholesterol and decreased levels of high-density lipoprotein cholesterol. Supplementing the diet of this group with acai caused a hypocholesterolemic effect by reducing total and non-high-density lipoprotein cholesterol. Serum levels of carbonyl proteins and total, free, and protein sulfhydryl groups were reduced by acai ingestion in animals receiving the standard or hypercholesterolemic diet. Acai supplementation induced a significant reduction in superoxide dismutase activity only in the hypercholesterolemic rats, indicating an association between diet and acai treatment. Also, acai supplementation increased paraoxonase activity in the CA and HA groups. CONCLUSION These results suggest that the consumption of acai improves antioxidant status and has a hypocholesterolemic effect in an animal model of dietary-induced hypercholesterolemia.

Iron overload alters glucose homeostasis, causes liver steatosis, and increases serum triacylglycerols in rats

The objective of this study was to investigate the effect of iron overload with a hyperlipidemic diet on the histologic feature of hepatic tissue, the lipid and glycemic serum profiles, and the markers of oxidative damage and stress in a rat model. Twenty-four male Fischer rats, purchased from Experimental Nutrition Laboratory, Federal University of Ouro Preto, were assigned to 4 equal groups, 2 were fed a standard cholesterol-free diet (group C or control and CI or control with iron) containing 8.0% soybean oil and 2 were fed a hyperlipidemic diet (group H or hyperlipidemic and HI or hyperlipidemic with iron) containing 1.0% cholesterol and 25.0% soybean oil. A total of 50 mg of iron was administered to rats in groups CI and HI in 5 equal doses (1 every 3 weeks for a 16-week period) by intraperitoneal injections of 0.1 mL of iron dextran solution (100 g Fe(2+)/L; Sigma, St Louis, Mo). The other rats in groups C and H were treated in a similar manner but with sterile saline (0.1 mL). Irrespective of the diet, iron excess enhanced serum triacylglycerols (P < .05) and reduced serum glucose and glycated hemoglobin levels (P < .05) but did not affect serum cholesterol concentration. Histologic analysis showed steatosis in groups H and to a lesser extent in HI. No significant differences (P > .05) were observed in paraoxonase activities or in serum levels of free or total sulfhydryl radicals, malondialdehyde, or total antioxidants. The findings suggest that iron excess in the rat probably modifies lipid metabolism and, as a consequence, alters glucose homeostasis and increases the level of serum triacylglycerols but not of cholesterol.

Vildagliptin Ameliorates Oxidative Stress and Pancreatic Beta Cell Destruction in Type 1 Diabetic Rats

BACKGROUND AND AIMS It is believed that oxidative stress plays a role in the pathogenesis of diabetes mellitus. Several strategies have been developed with the objective of minimizing diabetic complications. Among these, inhibitors of dipeptidyl peptidase-IV (DPP-IV), which act by blocking degradation of incretin hormones, glucagon-like peptide hormone (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP), have been the focus of many studies. It is known that, among the effects of incretins, we highlight its insulinotropic and cytoprotective effects on pancreatic β-cells. The objective of this study was to evaluate the possible protective effects of treatment with vildagliptin, a DPP-IV inhibitor, in β-cells in an experimental model of type 1 diabetes induced by streptozotocin (STZ). METHODS Rats were treated for 4 weeks with vildagliptin at concentrations of 5 and 10 mg/kg. In order to observe the pancreatic damage and the possible protective effects of vildagliptin treatment, we measured stress markers TBARS and protein carbonyl, antioxidant enzymes SOD and catalase, and analyzed pancreatic histology. RESULTS The treatment was effective in modulating stress in pancreatic tissue, both by reducing levels of stress markers as well as by increasing activity of SOD and catalase. After analyzing the pancreatic histology, we found that vildagliptin was also able to preserve islets and pancreatic β-cells, especially at the concentration of 5 mg/kg. CONCLUSION Thus, our results suggest that vildagliptin ameliorates oxidative stress and pancreatic beta cell destruction in type 1 diabetic rats. However, to evaluate the real potential of this medication in type 1 diabetes, further studies are needed.

Trypanosoma cruzi: Effect of benznidazole therapy combined with the iron chelator desferrioxamine in infected mice

Iron chelators have been employed in various studies aimed at evaluating the relationship between the iron status of the host and the development of infection. In the present study, the effects of benznidazole (BZ) therapy in combination with the iron chelator desferrioxamine (DFO) on the development of infection in mice inoculated with Trypanosoma cruzi Y strain have been investigated. Infected mice treated with DFO presented lower levels of parasitemia compared with infected untreated animals. Therapy with BZ for 21 days, with or without DFO, led to decreased parasitemia and reduced mortality, but BZ in combination with DFO treatment for 35 days (BZ/DFO-35) gave 0% mortality. All infected groups presented lower levels of iron in the liver, but serum iron concentrations were greater in DFO-35 and BZ/DFO-35, whereas hemoglobin levels were higher in BZ/DFO-35 and lower in DFO-35 compared with other treated groups. The percentage cure, determined from negative hemoculture and PCR results in animals that had survived for 60 days post-infection, was 18% for BZ and BZ/DFO-35, 42% for BZ combined with DFO for 21 days, and 67% for DFO-35. The results demonstrate that modification in iron stores increases BZ efficacy.

Efeito da estreptozotocina sobre os perfis glicêmico e lipídico e o estresse oxidativo em hamsters

OBJECTIVE: This study evaluated the effects of streptozotocin on glycemic and lipid profiles and oxidative stress status in hamsters. MATERIALS AND METHODS: Male Golden Syrian hamsters were divided in diabetic group (D) which received a streptozotocin single injection (STZ - 50 mg/kg), and control group (C) which received a single injection of the vehicle citrate buffer. Animals were euthanized after 10 days of experiment and blood, liver and kidneys were collected. RESULTS: The diabetic group had higher levels of glucose, triacylglycerols and cholesterol in serum and thiobarbituric acid reactive substances (TBARS) concentration increased in the liver and kidneys. Diabetes induced a significant increase in glutathione concentration in the liver and decreased paraoxonase and superoxide dismutase activities. CONCLUSION: Hamsters provide a novel animal model for diabetes mellitus and oxidative stress, similar to the human syndrome, which may be suitable for the testing of antidiabetic compounds.

Hypercholesterolemic diet induces hepatic steatosis and alterations in mRNA expression of NADPH oxidase in rat livers

OBJECTIVE This study aimed to determine whether a hypercholesterolemic diet induces hepatic steatosis, alterations in mRNA expression of NADPH oxidase subunits, and antioxidant defenses. MATERIALS AND METHODS Fischer rats were divided into two groups of eight animals according to the treatment, control (C) and hypercholesterolemic diet (H). Those in group C were fed a standard diet (AIN-93M), and those of the group H were fed a hypercholesterolemic diet (25% soybean oil and 1% cholesterol). RESULTS The hypercholesterolemic diet did not affect body weight, but resulted in the accumulation of lipids in the liver, increased serum activities of aminotransferases and cholesterol levels. Biomarker of lipid peroxidation (TBARS) and mRNA expression of NADPH oxidase subunits p22(phox) and p47(phox) were increased in the liver of animals in group H. Besides, the activity and expression of antioxidant enzymes were altered. CONCLUSION The results show increased mRNA expression of NADPH oxidase subunits and changes in antioxidant enzyme activities in diet-induced hepatic steatosis.

Trypanosoma cruzi: Desferrioxamine decreases mortality and parasitemia in infected mice through a trypanostatic effect

Desferrioxamine (DFO) is a potent iron chelator that is also known to modulate inflammation and act as an efficient antioxidant under normal conditions and under oxidative stress. Many in vitro and in vivo studies have shown the efficacy of DFO in the treatment of viral, bacterial and protozoan infections. DFO is known to reduce the intensity of Trypanosoma cruzi infections in mice even during a course of therapy that is not effective in maintaining anaemia or low iron levels. To further clarify these findings, we investigated the action of DFO on mouse T. cruzi infection outcomes and the direct impact of DFO on parasites. Infected animals treated with DFO (5 mg/animal/day) for 35 days, beginning 14 days prior to infection, presented lower parasitemia and lower cumulative mortality rate. No significant effect was observed on iron metabolism markers, erythrograms, leukograms or lymphocyte subsets. In the rapid method for testing in vivo T. cruzi susceptibility, DFO also induced lower parasitemia. In regard to its direct impact on parasites, DFO slightly inhibited the growth of amastigotes and trypomastigotes in fibroblast culture. Trypan blue staining showed no effects of DFO on parasite viability, and only minor apoptosis in trypomastigotes was observed. Nevertheless, a clear decrease in parasite mobility was detected. In conclusion, the beneficial actions of DFO on mice T. cruzi infection seem to be independent of host iron metabolism and free of significant haematological side effects. Through direct action on the parasite, DFO has more effective trypanostatic than trypanocidal properties.

Iron dextran increases hepatic oxidative stress and alters expression of genes related to lipid metabolism contributing to hyperlipidaemia in murine model.

The objective of this study was to investigate the effects of iron dextran on lipid metabolism and to determine the involvement of oxidative stress. Fischer rats were divided into two groups: the standard group (S), which was fed the AIN-93M diet, and the standard plus iron group (SI), which was fed the same diet but also received iron dextran injections. Serum cholesterol and triacylglycerol levels were higher in the SI group than in the S group. Iron dextran was associated with decreased mRNA levels of pparα, and its downstream gene cpt1a, which is involved in lipid oxidation. Iron dextran also increased mRNA levels of apoB-100, MTP, and L-FABP indicating alterations in lipid secretion. Carbonyl protein and TBARS were consistently higher in the liver of the iron-treated rats. Moreover, a significant positive correlation was found between oxidative stress products, lfabp expression, and iron stores. In addition, a negative correlation was found between pparα expression, TBARS, carbonyl protein, and iron stores. In conclusion, our results suggest that the increase observed in the transport of lipids in the bloodstream and the decreased fatty acid oxidation in rats, which was promoted by iron dextran, might be attributed to increased oxidative stress.

Oxidative stress causes hypertension and activation of nuclear factor-κB after high-fructose and salt treatments

There is evidence that diets rich in salt or simple sugars as fructose are associated with abnormalities in blood pressure regulation. However, the mechanisms underlying pathogenesis of salt- and fructose-induced kidney damage and/or consequent hypertension yet remain largely unexplored. Here, we tested the role of oxidative state as an essential factor along with high salt and fructose treatment in causing hypertension. Fischer male rats were supplemented with a high-fructose diet (20% in water) for 20 weeks and maintained on high-salt diet (8%) associate in the last 10 weeks. Fructose-fed rats exhibited a salt-dependent hypertension accompanied by decrease in renal superoxide dismutase activity, which is the first footprint of antioxidant inactivation by reactive oxygen species (ROS). Metabolic changes and the hypertensive effect of the combined fructose-salt diet (20 weeks) were markedly reversed by a superoxide scavenger, Tempol (10 mg/kg, gavage); moreover, Tempol (50 mM) potentially reduced ROS production and abolished nuclear factor-kappa B (NF-κB) activation in human embryonic kidney HEK293 cells incubated with L-fructose (30 mM) and NaCl (500 mosmol/kg added). Taken together, our data suggested a possible role of oxygen radicals and ROS-induced activation of NF-κB in the fructose- and salt-induced hypertension associated with the progression of the renal disease.

Açai (Euterpe oleracea Mart.) Upregulates Paraoxonase 1 Gene Expression and Activity with Concomitant Reduction of Hepatic Steatosis in High-Fat Diet-Fed Rats.

Açai (Euterpe oleracea Mart.), a fruit from the Amazon region, has emerged as a promising source of polyphenols. Açai consumption has been increasing owing to ascribed health benefits and antioxidant properties; however, its effects on hepatic injury are limited. In this study, we evaluated the antioxidant effect of filtered açai pulp on the expression of paraoxonase (PON) isoforms and PON1 activity in rats with nonalcoholic fatty liver disease (NAFLD). The rats were fed a standard AIN-93M (control) diet or a high-fat (HF) diet containing 25% soy oil and 1% cholesterol with or without açai pulp (2 g/day) for 6 weeks. Our results show that açai pulp prevented low-density lipoprotein (LDL) oxidation, increased serum and hepatic PON1 activity, and upregulated the expression of PON1 and ApoA-I in the liver. In HF diet-fed rats, treatment with açai pulp attenuated liver damage, reducing fat infiltration and triglyceride (TG) content. In rats receiving açai, increased serum PON1 activity was correlated with a reduction in hepatic steatosis and hepatic injury. These findings suggest the use of açai as a potential therapy for liver injuries, supporting the idea that dietary antioxidants are a promising approach to enhance the defensive systems against oxidative stress.