European Journal of Nutrition (v.47, #7)
Dehydroepiandrosterone (DHEA) prevents the prostanoid imbalance in mesenteric bed of fructose-induced hypertensive rats by Horacio A. Peredo; Marcos Mayer; Ileana R. Faya; Ana M. Puyó; Andrea Carranza (349-356).
In previous studies we reported an altered prostanoid (PR) release-pattern in mesenteric vessels in fructose (F)-overloaded rats, an experimental model of insulin resistance and hypertension. Dehydroepiandrosterone (DHEA) and its precursor Dehydroepiandrosterone sulfate (DHEA-S) are the most abundant circulating steroid hormones produced by the adrenal and recent studies in both cells and animals suggest that DHEA may have acute non-genomic actions that mimic both metabolic and vascular actions of insulin.This study was to analyze in F-overloaded rats, the effects of DHEA treatment on arterial blood pressure and the PR production in mesenteric vessels and aorta.Male 6 week-old Sprague–Dawley rats were randomly divided in four groups: a control group (C), a DHEA (30 mg/kg/sc/48 h)-treated group (D), a fructose (10% w/v in drinking water)-fed group (F), and both treatments simultaneously group (FD). The systolic blood pressure (SBP) was measured by tail cuff method and glycemia and triglyderidemia were measured by enzymatic assays. The mesenteric beds of all groups were dissected, and incubated in Krebs solution. The PR released were measured by HPLC.F overload increased SBP and triglyceridemia and decreased the mesenteric vasodilatory PR release. DHEA treatment prevented the increment in SBP and triglyceridemia and decreased vasoconstrictor PR in F-treated rats.DHEA normalize the PGI2/TX ratio, diminished in F-overloaded rats, through the decrease in thromboxane (TX) production and this could be one of the mechanisms by which DHEA prevented the slight hypertension in F-animals.
Keywords: DHEA; insulin resistance; hypertension; fructose; prostanoids
Maternal intake of fat, riboflavin and nicotinamide and the risk of having offspring with congenital heart defects by Huberdina P. M. Smedts; Maryam Rakhshandehroo; Anna C. Verkleij-Hagoort; Jeanne H. M. de Vries; Jaap Ottenkamp; Eric A. P. Steegers; Régine P. M. Steegers-Theunissen (357-365).
With the exception of studies on folic acid, little evidence is available concerning other nutrients in the pathogenesis of congenital heart defects (CHDs). Fatty acids play a central role in embryonic development, and the B-vitamins riboflavin and nicotinamide are co-enzymes in lipid metabolism.To investigate associations between the maternal dietary intake of fats, riboflavin and nicotinamide, and CHD risk in the offspring.A case-control family study was conducted in 276 mothers of a child with a CHD comprising of 190 outflow tract defects (OTD) and 86 non-outflow tract defects (non-OTD) and 324 control mothers of a non-malformed child. Mothers filled out general and food frequency questionnaires at 16 months after the index-pregnancy, as a proxy of the habitual food intake in the preconception period. Nutrient intakes (medians) were compared between cases and controls by Mann–Whitney U test. Odds ratios (OR) for the association between CHDs and nutrient intakes were estimated in a logistic regression model.Case mothers, in particular mothers of a child with OTD, had higher dietary intakes of saturated fat, 30.9 vs. 29.8 g/d; P < 0.05. Dietary intakes of riboflavin and nicotinamide were lower in mothers of a child with an OTD than in controls (1.32 vs. 1.41 mg/d; P < 0.05 and 14.6 vs. 15.1 mg/d; P < 0.05, respectively). Energy, unsaturated fat, cholesterol and folate intakes were comparable between the groups. Low dietary intakes of both riboflavin (<1.20 mg/d) and nicotinamide (<13.5 mg/d) increased more than two-fold the risk of a child with an OTD, especially in mothers who did not use vitamin supplements in the periconceptional period (OR 2.4, 95%CI 1.4–4.0). Increasing intakes of nicotinamide (OR 0.8, 95%CI 0.7–1.001, per unit standard deviation increase) decreased CHD risk independent of dietary folate intake.A maternal diet high in saturated fats and low in riboflavin and nicotinamide seems to contribute to CHD risk, in particular OTDs.
Keywords: congenital heart anomaly; saturated fat; B-vitamins; risk factors; prevention
Comparison of native or reformulated chicory fructans, or non-purified chicory, on rat cecal fermentation and mineral metabolism by Christian Demigné; Heidi Jacobs; Corinne Moundras; Marie-Jeanne Davicco; Marie-Noëlle Horcajada; Annick Bernalier; Véronique Coxam (366-374).
Chicory inulin has been identified as an effective prebiotic to promote active fermentation and lactobacilli proliferation in the large intestine, and to enhance calcium (Ca) digestive absorption and deposition in bones. The aim of this study was to compare, in a growing rat model, the effects on digestive fermentations and mineral metabolism of diets containing 7.5% inulin, using either a purified native inulin (NATInulin) or a reformulated inulin (REFInulin, based on a combination of short- and long chain fructans) or dehydrated chicory. All the inulin diets elicited a marked enlargement of the cecum and acidification of the cecal contents (P < 0.01) and these diets promoted succinic acid rich fermentation together with substantial amounts of short-chain fatty acids (SCFA), especially butyrate. After 1 month of adaptation, all the inulin diets strongly enhanced Ca absorption compared to controls (P < 0.01), but this effect was no more observed after 3 months of adaptation. Magnesium (Mg) absorption was stimulated by the inulin diets after 1 and 3 months experiment. Bone parameters were significantly affected by the chicory diet (enhanced distal bone mineral density and breaking load) whereas the purified inulin diets were less effective. In conclusion, with the present model, both NATInulin and REFInulin exerted similar effects as to (1) cecal fermentation and profile of end-products of bacterial metabolism, (2) stimulation of Ca and Mg digestive absorption and (3) overall effects on bone parameters. The particular effects of the chicory crude fractions on digestive fermentation and bone parameters suggest possible synergisms between inulin-type fructans and other nutrients.
Keywords: inulin; chicory; microflora; calcium; bone; rat
Six weeks phylloquinone supplementation produces undesirable effects on blood lipids with no changes in inflammatory and fibrinolytic markers in postmenopausal women by Mette Kristensen; Jane Kudsk; Susanne Bügel (375-379).
Cardiovascular disease is the major cause of death in the Western world, but some recent studies indicate that vitamin K may play a role in atherosclerosis protection.The aim of this study was to evaluate the effect of phylloquinone supplementation on blood lipids, inflammatory markers and fibrinolytic activity in postmenopausal women.Thirty-one postmenopausal women completed this placebo-controlled, randomized crossover study and received 500 µg phylloquinone or placebo in addition to their habitual diet during two periods of 6 weeks’ duration. Blood concentration of lipids, inflammatory markers and fibrinolytic parameters were measured after each period.Inflammatory markers, fibrinolytic parameters, total cholesterol and LDL-C were unaffected by the supplementation, whereas a 15% increase was seen in triacylglycerols (P = 0.015) and a 5% decrease in HDL-C (P = 0.06).Six weeks supplementation with a dose of phylloquinone similar to that obtainable from the diet induced a deterioration of the lipid profile with no improvement in any of the other risk markers analysed. Thus, these results do not support a cardioprotective effect of vitamin K as has been suggested by others.
Keywords: vitamin K; lipids; inflammation; cardiovascular disease; fibrinolytic activity
Differential inflammatory status in rats susceptible or resistant to diet-induced obesity: effects of EPA ethyl ester treatment by Nerea Pérez-Echarri; Patricia Pérez-Matute; Beatriz Marcos-Gómez; Maria J. Baena; Amelia Marti; J. Alfredo Martínez; María Jesus Moreno-Aliaga (380-386).
Obesity has been associated with a chronic low degree inflammatory response, characterized by an increase of inflammatory adipocytokines like tumoral necrosis factor-α (TNF-α), interleukin-6 (IL-6) as well as the synthesis of acute phase reactants such as haptoglobin.To evaluate if impairments in the inflammatory response at the white adipose tissue (WAT) level could be involved in the mechanisms conferring susceptibility or resistance to high-fat diet-induced obesity (DIO).The expression levels of WAT genes and systemic markers related to inflammation were evaluated in two groups of rats fed with a high-fat diet during 15 days that showed either an early susceptibility (DIO) or resistance (DR) to develop obesity. We also tested the efficacy of the eicosapentaenoic (EPA) ω-3 fatty acid treatment (35 days) to potentially counteract the obesity-associated inflammatory features in DIO rats.This trial showed that high-fat diet induces an increase on mRNA levels on TNF-α and haptoglobin in DIO animals (P < 0.05), while no significant changes were observed on DR rats. Furthermore, a significant increase in IL-6 mRNA (P < 0.05) was found in both DR and DIO rats. EPA-treatment caused a significant decrease in IL-6 mRNA (P < 0.05), without significant changes in haptoglobin mRNA levels in adipose tissue. An unexpected decrease was observed in haptoglobin serum levels (P < 0.05) in DIO rats, which was reverted to control values in EPA-treated animals.Our data suggest that obesity susceptibility or resistance may depend on the genetic make up related to inflammatory features, and support a role for ω-3 fatty acids in the prevention of obesity-associated inflammation in adipose tissue. In addition, our data do not support the hypothesis that serum haptoglobin is an acute phase protein expected to be positively related to increased adiposity in rats, at least in early and medium stages of DIO.
Keywords: inflammation; high-fat diet; susceptibility; resistance; eicosapentaenoic fatty acid (EPA); white adipose tissue (WAT)
Oxidative stress-induced insulin resistance in skeletal muscle cells is ameliorated by gamma-tocopherol treatment by Indu Singh; Andrew L. Carey; Nadine Watson; Mark A. Febbraio; John A. Hawley PhD (387-392).
Oxidative stress-induced reactive oxygen species are associated with the clinical manifestation of insulin resistance. Evidence suggests that antioxidant treatment may reduce this incidence.This study determined whether glucose oxidase (GO)-induced insulin resistance in cultured skeletal muscle cells could be ameliorated by pre-treatment with gamma-tocopherol (GT).Insulin sensitivity in L6 myotubes was assessed by 2-deoxy-d-[3H]-glucose uptake. The phosphorylation of distal insulin signaling proteins Akt and the Akt substrate AS160 were determined by western blot.One hour treatment with 100 mU/ml GO decreased insulin-stimulated glucose uptake (P < 0.001). Pre-treatment with GT either partially (100 µM) or completely (200 µM) restored insulin-stimulated glucose uptake in cells after GO-induced insulin resistance. GO-induced oxidative stress did not impair insulin stimulated phosphorylation of Akt or AS160, but 200 µM GT increased insulin-stimulated phosphorylation of these key signaling proteins (P < 0.05).High-dose (200 µM) GT treatment ameliorated oxidative stress-induced insulin resistance in cultured rat L6 skeletal muscle cells.
Keywords: glucose oxidase; L6 myotubes; Akt; AS160; glucose transport; antioxidants
Spirulina enhanced the skeletal muscle protein in growing rats by Fabrício A. Voltarelli; Maria Alice R. de Mello (393-400).
This study evaluates the effects of the blue green alga spirulina as the sole dietary source of protein on muscle protein in weaning rats.Young (30 days) Wistar rats were fed, during 60 days, with 17% protein spirulina (S) and compared to rats fed 17% protein casein (C). We evaluated the muscle total protein and DNA contents and the in vitro protein synthesis and degradation rates as well the myosin protein expression.The groups presented similar body weight (C = 427.3 ± 8.6; S = 434.6 ± 7.7 g) and length (C = 25.4 ± 0.2; S = 25.6 ± 0.2 cm). Soleus muscle total protein (C = 2.9 ± 0.1; S = 2.7 ± 0.1 mg/100 mg) and DNA (C = 0.084 ± 0.005; S = 0.074 ± 0.005 mg/100 mg) contents were also similar in both groups. Protein degradation (C = 427.5 ± 40.6; S = 476.7 ± 50.5 pmol/mg−1 h−1) did not differ between the groups but protein synthesis (C = 17.5 ± 1.0; S = 25.2 ± 1.9 pmol/mg−1 h−1) and myosin content (western blot analyses) were higher (P < 0.05, t test) in spirulina group.Although the spirulina proved adequate protein quality to maintain body growth, the muscle protein synthesis rates were increased by the ingestion of the experimental diet in young rats.
Keywords: skeletal muscle; spirulina ; protein
Ascorbic acid uptake affects ferritin, Dcytb and Nramp2 expression in Caco-2 cells by Nathalie M. Scheers; Ann-Sofie Sandberg (401-408).
Ascorbic acid (vitamin C) enhances iron uptake in human intestinal cells. It is commonly believed that the enhancement is due to the capacity of ascorbic acid to reduce ferric iron to ferrous iron. Other suggestions have recently been made about the effects of ascorbic acid on the cellular metabolism of iron. These effects must be investigated for several reasons. One important issue is to study whether ascorbic acid has effects on iron metabolism in the absence of extracellular iron in the intestinal lumen.The aim of this investigation was to determine whether cellular uptake of ascorbic acid affects iron acquisition in the Caco-2 cell line. The possible event was investigated by studying the expression of the iron storage protein ferritin, the iron uptake protein Nramp2 and a duodenal ferric reductase Dcytb after incubating ascorbic acid deficient or ascorbic acid fed cells with iron and/or ascorbic acid.The above stated interactions were studied in the human Caco-2 cell model. Cell lysates were collected and subjected to SDS-PAGE and Western blotting. The blotted samples were stained with specific antibodies (Rabbit α-human-Nramp2 and Goat α-human Dcytb) against the respective proteins and the bands achieved were analysed by reflective density measurements. The cellular ferritin content was analysed with a commercial kit and the intracellular ascorbic acid concentration was measured by HPLC.The results indicate that ascorbic acid uptake induces both iron independent and iron dependent ferritin formation, but the effect on iron dependent ferritin expression was significantly greater (470% compared to 19%). Western Blot analyses revealed a long term down-regulating effect of ascorbic acid on iron independent and iron dependent Nramp2 and Dcytb expression. However, the down-regulation of Dcytb was in general more extensive than that of Nramp2 (31–50% compared to 8–29%). In a second study of short term Nramp2 and Dcytb expression, the results suggested that both proteins were significantly up-regulated by ascorbic acid, regardless of intracellular ascorbic acid status. However, the impact of iron alone on Nramp2 up-regulation seems to be greater in the absence of ascorbic acid.The influence of intracellular ascorbic acid status on ferritin formation must be considered in iron uptake studies in Caco-2 cells. This could be a cause of diverging inter-laboratory results. The long term down-regulation of Nramp2 and Dcytb seems to correlate with results of human studies, where long term ascorbic acid supplementation does not affect iron status. Similarly, the short term up-regulation of Nramp2 and Dcytb seems to agree with the improvement in iron uptake shown in humans when single doses of ascorbic acid were administrated. These results are important for the understanding of the impact of ascorbic acid on iron status and will hopefully lead to further investigations on the matter.
Keywords: ascorbic acid; ferritin; Dcytb; Nramp2; Caco-2 cells
Increased dietary cholesterol does not increase plasma low density lipoprotein when accompanied by an energy-restricted diet and weight loss by Nicola L. Harman; Anthony R. Leeds; Dr. Bruce A. Griffin (408-408).