Maria Lúcia Pedrosa

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.

Dietary models for inducing hypercholesterolemia in rats

The present work aimed at finding a dietetical model capable of promoting the highest hypercholesterolemia without affecting the development of the rats. Sixty female Fisher rats were divided into five groups. The first one was fed a control diet; the remaining four were fed hypercholesterolemic diets with cholesterol and different contents of soybean oil, starch, casein, micronutrients and fiber and, consequently, different caloric values. After eight weeks animals were evaluated in relation to growth, fecal excretion, liver weight and fat, cholesterol and its fractions, serum biochemical parameters and sistolic pressure and compared with controls. The best result was obtained with the diet containing 25 % soybean oil, 1.0 % cholesterol, 13 % fiber and 4,538.4 Kcal/Kg, since it promoted an increase in LDL-cholesterol, a decrease in the HDL fraction and affected less the hepatic function of the animals.

Dietary açai modulates ROS production by neutrophils and gene expression of liver antioxidant enzymes in rats.

Açai (Euterpe oleracea Mart.) has recently emerged as a promising source of natural antioxidants. Because increased oxidative stress and impaired antioxidant defense mechanisms are important factors in the development of diabetic complications and many health claims have been reported for açai, the present study was undertaken to evaluate the possible protective effects of açai on the production of reactive oxygen species by neutrophils and on the liver antioxidant defense system in control and streptozotocin-induced diabetic rats. Diet supplementation with 2% açai was found to increase mRNA levels for gamma-glutamylcysteine synthetase and glutathione peroxidase in liver tissue and to decrease reactive oxygen species production by neutrophils. Compared to control animals, diabetic rats exhibited lower levels of mRNA coding for Zn-superoxide dismutase, glutathione peroxidase and gamma-glutamylcysteine synthetase and higher levels of reactive oxygen species production by neutrophils, thiobarbituric acid-reactive substances and carbonyl proteins in hepatic tissues. Although açai supplementation was not effective in restore gene expression of antioxidant enzymes in diabetic rats, it showed a protective effect, decreasing thiobarbituric acid-reactive substances levels and increasing reduced glutathione content in the liver. These findings suggest that açai can modulate reactive oxygen species production by neutrophils and that it has a significant favorable effect on the liver antioxidant defense system under fisiological conditions of oxidative stress and partially revert deleterious effects of diabetes in the liver.

The hypocholesterolemic activity of açaí (Euterpe oleracea Mart.) is mediated by the enhanced expression of the ATP-binding cassette, subfamily G transporters 5 and 8 and low-density lipoprotein receptor genes in the rat

Previous studies have demonstrated that the ingestion of açaí pulp can improve serum lipid profile in various animal models; therefore, we hypothesized that açaí pulp (Euterpe oleracea Mart.) may modulate the expression of the genes involved in cholesterol homeostasis in the liver and increase fecal excretion, thus reducing serum cholesterol. To test this hypothesis, we analyzed the expression of 7α-hydroxylase and ATP-binding cassette, subfamily G transporters (ABCG5 and ABCG8), which are genes involved with the secretion of cholesterol in the rat. We also evaluated the expression of sterol regulatory element-binding protein 2, 3-hydroxy-3-methylglutaryl CoA reductase, low-density lipoprotein receptor (LDL-R), and apolipoprotein B100, which are involved in cholesterol biosynthesis. Female Fischer rats were divided into 4 groups: the C group, which was fed a standard AIN-93 M diet; the CA group, which was fed a standard diet supplemented with 2% açaí pulp; the H group, which was fed a hypercholesterolemic diet (25% soy oil and 1% cholesterol); and the HA group, which was fed a hypercholesterolemic diet supplemented with 2% açaí pulp. At the end of the experimental period, the rats were euthanized, and their blood and livers were collected. The HA group exhibited a significant decrease in serum total cholesterol, low-density lipoprotein cholesterol, and atherogenic index and also had increased high-density lipoprotein cholesterol and cholesterol excretion in feces compared with the H group. In addition, the expression of the LDL-R, ABCG5, and ABCG8 genes was significantly increased by the presence of açaí pulp. These results suggest that açaí pulp promotes a hypocholesterolemic effect in a rat model of dietary-induced hypercholesterolemia through an increase in the expression of ATP-binding cassette, subfamily G transporters, and LDL-R genes.

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.

Rosiglitazone-induced heart remodelling is associated with enhanced turnover of myofibrillar protein and mTOR activation

We investigated cardiac hypertrophy elicited by rosiglitazone treatment at the level of protein synthesis/degradation, mTOR, MAPK and AMPK signalling pathways, cardiac function and aspects of carbohydrate/lipid metabolism. Hearts of rats treated or not with rosiglitazone (15 mg/kg day) for 21 days were evaluated for gene expression, protein synthesis, proteasome and calpain activities, signalling pathways, and function by echocardiography. Rosiglitazone induced eccentric heart hypertrophy associated with increased expression of ANP, BNP, collagen I and III and fibronectin, reduced heart rate and increased stroke volume. Rosiglitazone robustly increased heart glycogen content ( approximately 400%), an effect associated with increases in glycogenin and UDPG-PPL mRNA levels and glucose uptake, and a reduction in glycogen phosphorylase expression and activity. Cardiac triglyceride content, lipoprotein lipase activity and mRNA levels of enzymes involved in fatty acid oxidation were also reduced by the agonist. Rosiglitazone-induced cardiac hypertrophy was associated with an increase in myofibrillar protein content and turnover (increased synthesis and an enhancement of calpain-mediated myofibrillar degradation). In contrast, 26S beta5 chymotryptic proteasome activity and mRNA levels of 20S beta2 and beta5 and 19S RPN 2 proteasome subunits along with the ubiquitin ligases atrogin and CHIP were all reduced by rosiglitazone. These morphological and biochemical changes were associated with marked activation of the key growth-promoting mTOR signalling pathway, whose pharmacological inhibition with rapamycin completely blocked cardiac hypertrophy induced by rosiglitazone. The study demonstrates that both arms of protein balance are involved in rosiglitazone-induced cardiac hypertrophy, and establishes the mTOR pathway as a novel important mediator therein.

Protein‐energy malnutrition decreases immune response to Leishmania chagasi vaccine in BALB/c mice

Protein‐energy malnutrition and visceral leishmaniasis are important problems of public health affecting millions of people worldwide. Vaccine efficacy depends on the ability of individuals to mount an appropriate immune response and may be inadequate in malnourished persons. In this study, we used a mouse model to verify the effect of combined protein, iron and zinc deficiency in the response to Leishmania chagasi antigen vaccine. BALB/c mice were fed with a low‐protein (3% casein), iron‐ and zinc‐deficient diet or control diet (14% casein and sufficient in zinc and iron). After malnutrition establishment, mice were vaccinated subcutaneously with L. chagasi Ag plus saponin. After vaccination, mice were nutritionally repleted and then all mice were challenged with L. chagasi promastigotes. Four weeks later, liver and spleen parasite load was evaluated. Our data show that vaccine caused a significant reduction in parasite load in spleen and liver from mice fed with control diet. However, splenic parasitism was increased in mice fed with deficient diet and this diet caused a reduction in splenocyte IFN‐γ production in response to the vaccine in repleted mice. These data suggest that malnutrition may alter immune response to L. chagasi vaccine in BALB/c model of infection, even after nutritional repletion.

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.

A Low Protein Diet Causes an Increase in the Basal Levels and Variability of Mean Arterial Pressure and Heart Rate in Fisher Rats

Abstract The correlation between nutrition and cardiovascular related disorders is a well-established fact. Previous work from our Laboratory has suggested a significant compromise of cardiovascular reflexes in conscious rats submitted to a low-protein (LP) diet. Our working hypothesis is that the basal level of mean arterial pressure (MAP), variability of the mean arterial pressure (VMAP), heart rate (HR) and variability of heart rate (VHR) are altered in rats submitted to a protein restricted diet. Two experimental groups were used: control group (normal protein 15%, NP) and malnourished group (low-protein 6%, LP). In order to verify the efficiency of the dietary restriction we measured body weight, total blood protein, plasma albumin, urea and glucose. Our experiments demonstrated that the malnourished rats presented augment levels of basal MAP (LP 122±2 mmHg vs. NP 113±1 mmHg) and of VMAP (LP 12.8±1.5 mmHg vs. NP 9±1 mmHg) when compared to the control group. We observed similar increased levels, in the malnourished group, for both HR (LP 429±8 bpm vs. NP 381±7 bpm) and VHR (LP 67.6±8.3 bpm vs. NP 44.4±4.9 bpm). Our results suggest a correlation between the LP diet in Fisher rats and the increased basal levels of mean arterial pressure, HR and their respective variability.

Immune response to Leishmania (Leishmania) chagasi infection is reduced in malnourished BALB/c mice

Protein-energy malnutrition and micronutrient deficiencies may down-regulate immune response and increase morbidity and mortality due to infection. In this study, a murine model was used to study the effects of protein, iron and zinc deficiencies on the immune response to Leishmania (Leishmania) chagasi infection. Mice were initially fed a standard diet or with a diet containing 3% casein but deficient in zinc and iron. After malnutrition was established, mice were inoculated with L. chagasi and sacrificed four weeks later in order to evaluate liver and spleen parasite loads and serum biochemical parameters. Significant decreases in liver and spleen weight, an increase in the parasite loads in these organs and decreases in serum protein and glucose concentrations in malnourished animals were observed. Furthermore, the production of interferon-gamma by spleen cells from infected malnourished mice stimulated by Leishmania antigen was significantly lower compared with that in control diet mice. These data suggest that malnutrition alters the immune response to L. chagasi infection in the BALB/c model and, in association with the effects on biochemical and anatomical parameters of the host, favored increases in the parasite loads in the spleens and livers of these animals.