Influences of alpha-tocopherol on cholesterol metabolism and fatty streak development in apolipoprotein E-deficient mice fed an atherogenic diet

Although the role of oxidized lipoproteins is well known in atherogenesis, the role of vitamin E supplementation is still controversial. There is also little information about cholesterol metabolism (hepatic concentration and fecal excretion) in the new models of atherosclerosis. In the present study, we evaluated the effect of moderate vitamin E supplementation on cholesterol metabolism and atherogenesis in apolipoprotein E (apo E)-deficient mice. Apo E-deficient mice were fed an atherogenic diet containing 40 or 400 mg/kg of alpha-tocopherol acetate for 6 weeks. Total cholesterol in serum and liver and 3-OH-alpha-sterols in feces, and fecal excretion of bile acids were determined and histological analyses of aortic lesion were performed. A vitamin E-rich diet did not affect body weight, food intake or serum cholesterol. Serum and hepatic concentrations of cholesterol as well as sterol concentration in feces were similar in both groups. However, when compared to controls, the alpha-tocopherol-treated mice showed a reduction of about 60% in the atherosclerotic lesions when both the sum of lesion areas and the average of the largest lesion area were considered. These results demonstrate that supplementation of moderate doses of alpha-tocopherol was able to slow atherogenesis in apo E-deficient mice and to reduce atherogenic lipoproteins without modifying the hepatic pool or fecal excretion of cholesterol and bile acids.

Low pH and calcium effects on net Na+ and K+ fluxes in two catfish species from the Amazon River (Corydoras: Callichthyidae)

The present study analyzes Na+ and K+ disturbances caused by low pH in two catfish species from the Amazon River. Corydoras adolfoi inhabits ion-poor, black-stained, low pH (3.5-4.0) waters, while C. schwartzi is native to ion-rich waters at circumneutral pH. Fish were exposed to pH 3.5 Ca2+-free, and Ca2+-enriched (~500 µmol/l) water to determine the protective effects of calcium. Net Na+ and K+ fluxes were measured in the water collected from the fish experimental chambers. C. adolfoi was unable to control the Na+ efflux at low pH, exhibiting Na+ loss up to -594 ± 84 nmol g-1 h-1 during the first hour. After 3 and 6 h, net Na+ flux increased by 7- and 23-fold, respectively. In C. schwartzi, at pH 3.5, the initial high Na+ loss (-1,063 ± 73 nmol g-1 h-1) was gradually attenuated. A K+ loss occurred in both species, but remained relatively constant throughout exposure. High [Ca2+] affected ion losses in both species. C. adolfoi had 70% loss attenuation, indicating incapacity to control Na+ efflux. In C. schwartzi, elevated [Ca2+] completely prevented the Na+ losses caused by exposure to low pH. Rather different patterns were seen for K+ fluxes, with C. adolfoi showing no K+ disruption when exposed to low pH/high [Ca2+]. Thus, C. adolfoi loses Na+ during acid exposure, but has the ability to control K+ loss, while C. schwartzi controls diffusive Na+ loss but exhibits a slightly higher K+ loss. Ion balance was influenced by [Ca2+] at low pH in C. schwartzi but not in C. adolfoi.

Effect of a Brazilian regional basic diet on the prevalence of caries in rats

The aim of the present study was to determine the effect of a regional basic diet (RBD) on the prevalence of caries in the molar teeth of rats of both sexes aged 23 days. The animals were divided into six groups of 10 rats each receiving the following diets for 30 and 60 days after weaning: RBD, a cariogenic diet, and a commercial diet. The prevalence and penetration of caries in the molar teeth of the rats was then analyzed. The RBD produced caries in 37.5% of the teeth of animals fed 30 days, and in 83.4% of animals fed 60 days, while the cariogenic diet produced caries in 72.5% and 77.5% of the teeth of animals fed 30 and 60 days, respectively. Rats fed the RBD for 30 days had caries in the enamel in 38% of their teeth, 48% had superficial dentin caries, and 7.5% moderate dentin caries. The effect of the RBD did not differ significantly from that of the cariogenic diet in terms of the presence of caries in rats fed 60 days. The penetration depth of the caries produced by the RBD was the same as that produced by the cariogenic diet. Our results show that the RBD has the same cariogenic potential as the cariogenic diet. Since the RBD is the only option for the low-income population, there should be a study of how to compensate for the cariogenicity of this diet.

Diet plus insulin compared to diet alone in the treatment of gestational diabetes mellitus: a systematic review

Fetuses of mothers with gestational diabetes mellitus are at increased risk to develop perinatal complications mainly due to macrosomia. However, in view of the marked heterogeneity of this disease, it seems difficult to set guidelines for diagnosis and treatment. This complicates the choice of assigning patients either to diet or to insulin therapy. Also of concern is how much benefit could be expected from insulin therapy in preventing fetal complications in these patients. In a systematic review of the literature assessing the efficacy of insulin in preventing macrosomia in fetuses of mothers with gestational diabetes, we found six randomized controlled trials comparing diet alone to diet plus insulin. The studies included a total of 1281 patients (644 in the diet plus insulin group and 637 in the diet group), with marked differences among trials concerning diagnostic criteria, randomization process and treatment goals. Meta-analysis of the data resulted in a risk difference of -0.098 (95%CI: -0.168 to -0.028), and a number-necessary-to-treat of 11 (95%CI: 6 to 36), which means that it is necessary to treat 11 patients with insulin to prevent one case of macrosomia. This indicates a potential benefit of insulin, but not significantly enough to set treatment guidelines. Because of the heterogeneous evidence available in the literature about this matter, we conclude that larger trials addressing the efficacy of these two therapeutic modalities in preventing macrosomia are warranted.

A leucine-supplemented diet improved protein content of skeletal muscle in young tumor-bearing rats

Cancer cachexia induces host protein wastage but the mechanisms are poorly understood. Branched-chain amino acids play a regulatory role in the modulation of both protein synthesis and degradation in host tissues. Leucine, an important amino acid in skeletal muscle, is higher oxidized in tumor-bearing animals. A leucine-supplemented diet was used to analyze the effects of Walker 256 tumor growth on body composition in young weanling Wistar rats divided into two main dietary groups: normal diet (N, 18% protein) and leucine-rich diet (L, 15% protein plus 3% leucine), which were further subdivided into control (N or L) or tumor-bearing (W or LW) subgroups. After 12 days, the animals were sacrificed and their carcass analyzed. The tumor-bearing groups showed a decrease in body weight and fat content. Lean carcass mass was lower in the W and LW groups (W = 19.9 ± 0.6, LW = 23.1 ± 1.0 g vs N = 29.4 ± 1.3, L = 28.1 ± 1.9 g, P < 0.05). Tumor weight was similar in both tumor-bearing groups fed either diet. Western blot analysis showed that myosin protein content in gastrocnemius muscle was reduced in tumor-bearing animals (W = 0.234 ± 0.033 vs LW = 0.598 ± 0.036, N = 0.623 ± 0.062, L = 0.697 ± 0.065 arbitrary intensity, P < 0.05). Despite accelerated tumor growth, LW animals exhibited a smaller reduction in lean carcass mass and muscle myosin maintenance, suggesting that excess leucine in the diet could counteract, at least in part, the high host protein wasting in weanling tumor-bearing rats.

Screening of antibacterial extracts from plants native to the Brazilian Amazon Rain Forest and Atlantic Forest

More than 20% of the world's biodiversity is located in Brazilian forests and only a few plant extracts have been evaluated for potential antibacterial activity. In the present study, 705 organic and aqueous extracts of plants obtained from different Amazon Rain Forest and Atlantic Forest plants were screened for antibacterial activity at 100 µg/ml, using a microdilution broth assay against Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Escherichia coli. One extract, VO581, was active against S. aureus (minimum inhibitory concentration (MIC) = 140 µg/ml and minimal bactericidal concentration (MBC) = 160 µg/ml, organic extract obtained from stems) and two extracts were active against E. faecalis, SM053 (MIC = 80 µg/ml and MBC = 90 µg/ml, organic extract obtained from aerial parts), and MY841 (MIC = 30 µg/ml and MBC = 50 µg/ml, organic extract obtained from stems). The most active fractions are being fractionated to identify their active substances. Higher concentrations of other extracts are currently being evaluated against the same microorganisms.

Hypercaloric cafeteria-like diet induced UCP3 gene expression in skeletal muscle is impaired by hypothyroidism

The uncoupling protein UCP3 belongs to a family of mitochondrial carriers located in the inner mitochondrial membrane of certain cell types. It is expressed almost exclusively at high levels in skeletal muscle and its physiological role has not been fully determined in this tissue. In the present study we have addressed the possible interaction between a hypercaloric diet and thyroid hormone (T3), which are strong stimulators of UCP3 gene expression in skeletal muscle. Male Wistar rats weighing 180 ± 20 g were rendered hypothyroid by thyroidectomy and the addition of methimazole (0.05%; w/v) to drinking water after surgery. The rats were fed a hypercaloric cafeteria diet (68% carbohydrates, 13% protein and 18% lipids) for 10 days and sacrificed by decapitation. Subsequently, the gastrocnemius muscle was dissected, total RNA was isolated with Trizol™ and UCP3 gene expression was determined by Northern blotting using a specific probe. Statistical analysis was performed by one-way analysis of variance (ANOVA) followed by the Student-Newman-Keuls post-test. Skeletal muscle UCP3 gene expression was decreased by 60% in hypothyroid rats and UCP3 mRNA expression was increased 70% in euthyroid cafeteria-fed rats compared to euthyroid chow-fed animals, confirming previous studies. Interestingly, the cafeteria diet was unable to stimulate UCP3 gene expression in hypothyroid animals (40% lower as compared to euthyroid cafeteria-fed animals). The results show that a hypercaloric diet is a strong stimulator of UCP3 gene expression in skeletal muscle and requires T3 for an adequate action.

Effects of diet and exercise training on neurovascular control during mental stress in obese women

Since neurovascular control is altered in obese subjects, we hypothesized that weight loss by diet (D) or diet plus exercise training (D + ET) would improve neurovascular control during mental stress in obese women. In a study with a dietary reduction of 600 kcal/day with or without exercise training for 4 months, 53 obese women were subdivided in D (N = 22, 33 ± 1 years, BMI 34 ± 1 kg/m²), D + ET (N = 22, 33 ± 1 years, BMI 33 ± 1 kg/m²), and nonadherent (NA, N = 9, 35 ± 2 years, BMI 33 ± 1 kg/m²) groups. Muscle sympathetic nerve activity (MSNA) was measured by microneurography and forearm blood flow by venous occlusion plethysmography. Mental stress was elicited by a 3-min Stroop color word test. Weight loss was similar between D and D + ET groups (87 ± 2 vs 79 ± 2 and 85 ± 2 vs 76 ± 2 kg, respectively, P < 0.05) with a significant reduction in MSNA during mental stress (58 ± 2 vs 50 ± 2, P = 0.0001, and 59 ± 3 vs 50 ± 2 bursts/100 beats, P = 0.0001, respectively), although the magnitude of the response was unchanged. Forearm vascular conductance during mental stress was significantly increased only in D + ET (2.74 ± 0.22 vs 3.52 ± 0.19 units, P = 0.02). Weight loss reduces MSNA during mental stress in obese women. The increase in forearm vascular conductance after weight loss provides convincing evidence for D + ET interventions as a nonpharmacologic therapy of human obesity.

Comparative study of human exposure to mercury in riverside communities in the Amazon region

Four populations in the Amazon area were selected for a comparative study of mercury-exposed and non-exposed populations: São Luiz do Tapajós, Barreiras, Panacauera, and Pindobal Grande. The highest mercury levels in human hair samples were found in São Luiz do Tapajós and Barreiras, greatly exceeding the limits established by the World Health Organization. Panacauera showed an intermediate level below 9 µg/g. This was the first comparative and simultaneous evaluation of mercury exposure in the Amazon area. Also, thanks to this type of monitoring, we were able to eliminate the uncertainties about the reference dose. On the basis of these data, we can conclude that the mercury levels detected in exposed populations of the Tapajós River basin may be dangerous not only because they are above the World Health Organization limits, but also because the simultaneous mercury detection in non-exposed populations with similar characteristics provided a valid control and revealed lower mercury levels. Our results support the importance of continuous monitoring in both exposed and non-exposed populations.

Etiology of diarrheal infections in children of Porto Velho (Rondonia, Western Amazon region, Brazil)

In the present study, 470 children less than 72 months of age and presenting acute diarrhea were examined to identify associated enteropathogenic agents. Viruses were the pathogens most frequently found in stools of infants with diarrhea, including 111 cases of rotavirus (23.6% of the total diarrhea cases) and 30 cases of adenovirus (6.3%). The second group was diarrheogenic Escherichia coli (86 cases, 18.2%), followed by Salmonella sp (44 cases, 9.3%) and Shigella sp (24 cases, 5.1%). Using the PCR technique to differentiate the pathogenic categories of E. coli, it was possible to identify 29 cases (6.1%) of enteropathogenic E. coli (EPEC). Of these, 10 (2.1%) were typical EPEC and 19 (4.0%) atypical EPEC. In addition, there were 26 cases (5.5%) of enteroaggregative E. coli, 21 cases (4.4%) of enterotoxigenic E. coli, 7 cases (1.4%) of enteroinvasive E. coli (EIEC), and 3 cases (0.6%) of enterohemorrhagic E. coli. When comparing the frequencies of diarrheogenic E. coli, EPEC was the only category for which significant differences were found between diarrhea and control groups. A low frequency of EIEC was found, thus EIEC cannot be considered to be a potential etiology agent of diarrhea. Simultaneous infections with two pathogens were found in 39 diarrhea cases but not in controls, suggesting associations among potential enteropathogens in the etiology of diarrhea. The frequent association of diarrheogenic E. coli strains was significantly higher than the probability of their random association, suggesting the presence of facilitating factor(s).

Behavioral changes induced by cocaine in mice are modified by a hyperlipidic diet or recombinant leptin

The objective of the present study was to determine if the acute behavioral effects of cocaine acutely administered intraperitoneally (ip) at doses of 5, 10 and 20 mg/kg on white male CF1 mice, 90 days of age, would be influenced by leptin acutely administered ip (at doses of 5, 10 and 20 µg/kg) or by endogenous leptin production enhanced by a high-fat diet. The acute behavioral effects of cocaine were evaluated in open-field, elevated plus-maze and forced swimming tests. Results were compared between a group of 80 mice consuming a balanced diet and a high-fat diet, and a group of 80 mice fed a commercially available rodent chow formula (Ralston Purina) but receiving recombinant leptin (rLeptin) or saline ip. Both the high-fat-fed and rLeptin-treated mice showed decreased locomotion in the open-field test, spent more time in the open arms of the elevated plus-maze and showed less immobility time in the forced swimming test (F(1,68) = 7.834, P = 0.007). There was an interaction between diets and cocaine/saline treatments in locomotion (F(3,34) = 3.751, P = 0.020) and exploration (F(3,34) = 3.581, P = 0.024). These results suggest that anxiolytic effects and increased general activity were induced by leptin in cocaine-treated mice and that low leptin levels are associated with behavioral depression. Chronic changes in diet composition producing high leptin levels or rLeptin treatment may result in an altered response to cocaine in ethologic tests that measure degrees of anxiety and depression, which could be attributed to an antagonistic effect of leptin.

Mercury toxicity in the Amazon: contrast sensitivity and color discrimination of subjects exposed to mercury

We measured visual performance in achromatic and chromatic spatial tasks of mercury-exposed subjects and compared the results with norms obtained from healthy individuals of similar age. Data were obtained for a group of 28 mercury-exposed subjects, comprising 20 Amazonian gold miners, 2 inhabitants of Amazonian riverside communities, and 6 laboratory technicians, who asked for medical care. Statistical norms were generated by testing healthy control subjects divided into three age groups. The performance of a substantial proportion of the mercury-exposed subjects was below the norms in all of these tasks. Eleven of 20 subjects (55%) performed below the norms in the achromatic contrast sensitivity task. The mercury-exposed subjects also had lower red-green contrast sensitivity deficits at all tested spatial frequencies (9/11 subjects; 81%). Three gold miners and 1 riverine (4/19 subjects, 21%) performed worse than normal subjects making more mistakes in the color arrangement test. Five of 10 subjects tested (50%), comprising 2 gold miners, 2 technicians, and 1 riverine, performed worse than normal in the color discrimination test, having areas of one or more MacAdam ellipse larger than normal subjects and high color discrimination thresholds at least in one color locus. These data indicate that psychophysical assessment can be used to quantify the degree of visual impairment of mercury-exposed subjects. They also suggest that some spatial tests such as the measurement of red-green chromatic contrast are sufficiently sensitive to detect visual dysfunction caused by mercury toxicity.

Effect of a cholesterol-rich diet on the metabolism of the free and esterified cholesterol components of a nanoemulsion that resembles LDL in rabbits

We have shown that the free cholesterol (FC) and the cholesteryl ester (CE) moieties of a nanoemulsion with lipidic structure resembling low-density lipoproteins show distinct metabolic fate in subjects and that this may be related to the presence of dyslipidemia and atherosclerosis. The question was raised whether induction of hyperlipidemia and atherosclerosis in rabbits would affect the metabolic behavior of the two cholesterol forms. Male New Zealand rabbits aged 4-5 months were allocated to a control group (N = 17) fed regular chow and to a 1% cholesterol-fed group (N = 13) during a 2-month period. Subsequently, the nanoemulsion labeled with ³H-FC and 14C-CE was injected intravenously for the determination of plasma kinetics and tissue uptake of the radioactive labels. In controls, FC and CE had similar plasma kinetics (fractional clearance rate, FCR = 0.234 ± 0.056 and 0.170 ± 0.038 h-1, respectively; P = 0.065). In cholesterol-fed rabbits, the clearance of both labels was delayed and, as a remarkable feature, FC-FCR (0.089 ± 0.033 h-1) was considerably greater than CE-FCR (0.046 ± 0.010 h-1; P = 0.026). In the liver, the major nanoemulsion uptake site, uptake of the labels was similar in control animals (FC = 0.2256 ± 0.1475 and CE = 0.2135 ± 0.1580%/g) but in cholesterol-fed animals FC uptake (0.0890 ± 0.0319%/g) was greater than CE uptake (0.0595 ± 0.0207%/g; P < 0.05). Therefore, whereas in controls, FC and CE have similar metabolism, the induction of dyslipidemia and atherosclerosis resulted in dissociation of the two forms of cholesterol.

Effect of praziquantel administration on hepatic stereology of mice infected with Schistosoma mansoni and fed a low-protein diet

A study was undertaken to investigate the effect of administering praziquantel (PZQ), focusing on the liver stereological findings of malnourished mice infected with Schistosoma mansoni. Thirty female Swiss Webster mice (age: 21 days; weight: 8-14 g) were fed either a low-protein diet (8%) or standard chow (22% protein) for 15 days. Five mice in each group were infected with 50 cercariae each of the BH strain (Brazil). PZQ therapy (80 mg/kg body weight, per day) was started on the 50th day of infection and consisted of daily administration for 5 days. Volume density (hepatocytes, sinusoids and hepatic fibrosis) was determined by stereology using a light microscope. Body weight gain and total serum albumin levels were always lower in undernourished mice. Our stereological study demonstrated that treatment increased both volume density of hepatocytes in mice fed standard chow (47.56%, treated group and 12.06%, control) and low-protein chow (30.98%, treated group and 21.44%, control), and hepatic sinusoids [standard chow (12.52%, treated group and 9.06%, control), low-protein chow (14.42%, treated group and 8.46%, control)], while hepatic fibrosis was reduced [standard chow (39.92%, treated group and 78.88%, control) and low-protein chow (54.60%, treated group and 70.10%, control)]. On the other hand, mice fed low-protein chow decreased density volume of hepatocytes and hepatic fibrosis. In conclusion, our findings indicate that treatment with PZQ ameliorates hepatic schistosomiasis pathology even in mice fed a low-protein diet.