Journal of Nutrition Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Sodium-Dependent Phosphate Uptake in the Jejunum Is Post-Transcriptionally Regulated in Pigs Fed a Low-Phosphorus Diet and Is Independent of Dietary Calcium Concentration [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Saddoris, K. L., Fleet, J. C., Radcliffe, J. S. — Fri, 19 Mar 2010 09:01:14 PDT

In rodents, severe dietary P restriction increases active phosphate absorption by the intestine. However, it remains unknown if moderate dietary P restriction has a similar effect. Weanling pigs (n = 32; body weight 7.4 ± 0.55 kg) were used in a 2 x 2 factorial design and fed dietary available P (aP) concentrations of 0.23 or 0.40% and Ca concentrations of 0.58 or 1.00% for 14 d. Diets were formulated on an aP basis instead of a total P basis, because pigs are unable to absorb phytate-P present in corn and soybean meal. Jejunal segments were mounted in modified Ussing chambers for determination of Na⁺-dependent nutrient transport. Intestinal mucosal scrapings were taken for RNA isolation and brush border membrane (BBM) vesicle isolation. Na⁺-dependent phosphate uptake and gene expression of Na-phosphate cotransporter IIb (NaPi-IIb), SGLT-1 (sodium/glucose cotransporter-1), and calbindin D(9k) and protein expression of NaPi-IIb were evaluated. Na⁺-dependent phosphate transport increased (P < 0.05) 46% as dietary aP concentration was decreased. However, increased Na⁺-dependent phosphate uptake was not accompanied by increased NaPi-IIb mRNA expression. Expression of NaPi-IIb protein in the BBM increased (P < 0.01) 84% in pigs fed low-P diets compared with pigs fed adequate-P diets. No dietary Ca effects or aP x Ca interactions were detected for Na-dependent P uptake, mRNA or protein expression of NaPi-IIb, or mRNA expression of calbindin D(9k). These data suggest that restricting dietary aP concentration by only 43% stimulates Na⁺-dependent phosphate uptake and expression of the NaPi-IIb protein in the BBM of the small intestine and through a post-transcriptional mechanism.

A Psyllium Fiber-Enriched Meal Strongly Attenuates Postprandial Gastrointestinal Peptide Release in Healthy Young Adults [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Fri, 19 Mar 2010 09:01:14 PDT

Dietary fiber (DF) and protein are essential constituents of a healthy diet and are well known for their high satiety impact. However, little is known about their influence on postprandial gastrointestinal (GI) peptide release. Our aim in this single-blind, randomized, cross-over study was to investigate the effects of DF and/or protein enrichments on satiety-related metabolic and hormonal responses. Sixteen healthy, nonobese volunteers participated in the study and ingested 1 of 5 isoenergetic test meals in a randomized order on separate days. The test meals were as follows: 1) low in protein (2.8 g) and fiber (7.6 g); 2) low in protein (2.6 g) and high in soluble fiber (psyllium, 23.0 g); 3) high in protein (soy, 19.7 g) and low in fiber (6.2 g); 4) high in protein (18.4 g) and fiber (23.0 g); and 5) white wheat bread. Serum insulin and plasma glucose, ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) concentrations were determined for 2 h following the meals. In addition, hunger and satiety ratings were collected. Postprandial glucose, insulin, ghrelin, GLP-1, and PYY responses all differed among the meals (P ≤ 0.05). Fiber-enriched meals decreased glucose, insulin, ghrelin, and PYY responses; in addition, PYY secretion was prolonged compared with the other meals. The postprandial GLP-1 concentration was significantly suppressed after a fiber- and protein-rich meal, in contrast to the initial increases following the other meals. However, postprandial ratings of appetite were mostly similar after the test meals. In conclusion, solid meals enriched with psyllium fiber strongly modified postprandial signals arising from the GI tract.

Acute Energy Deprivation Affects Skeletal Muscle Protein Synthesis and Associated Intracellular Signaling Proteins in Physically Active Adults [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Fri, 19 Mar 2010 09:01:14 PDT

To date, few studies have characterized the influence of energy deprivation on direct measures of skeletal muscle protein turnover. In this investigation, we characterized the effect of an acute, moderate energy deficit (10 d) on mixed muscle fractional synthetic rate (FSR) and associated intracellular signaling proteins in physically active adults. Eight men and 4 women participated in a 20-d, 2-phase diet intervention study: weight maintenance (WM) and energy deficient (ED; ~80% of estimated energy requirements). Dietary protein (1.5 g · kg^–1 · d^–1) and fat (~30% of total energy) were constant for WM and ED. FSR and intracellular signaling proteins were measured on d 10 of both interventions using a primed, constant infusion of [²H₅]-phenylalanine and Western blotting techniques, respectively. Participants lost ~1 kg body weight during ED (P < 0.0001). FSR was reduced ~19% (P < 0.05) for ED (0.06 ± 0.01%/h) compared with WM (0.074 ± 0.01%/h). Protein kinase B and eukaryotic initiation factor 4E binding protein 1 phosphorylation were lower (P < 0.05) during ED compared with WM. AMP activated protein kinase phosphorylation decreased (P < 0.05) over time regardless of energy status. These findings show that FSR and associated synthetic intracellular signaling proteins are downregulated in response to an acute, moderate energy deficit in physically active adults and provide a basis for future studies assessing the impact of prolonged, and perhaps more severe, energy restriction on skeletal muscle protein turnover.

Postnatal Hepatic Fatty Acid Oxidative Capacity of Preterm Pigs Receiving TPN Does Not Differ from That of Term Pigs and Is Not Affected by Supplemental Arachidonic and Docosahexaenoic Acids [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Campbell, J. A., Martin, J. E., Melendez, K., Stout, M. B., Lyvers-Peffer, P. A. — Fri, 19 Mar 2010 09:01:14 PDT

To improve pediatric care of preterm infants, a better understanding of the metabolic processes associated with immaturity is needed. To this end, preterm and term pigs were delivered and administered either a control, a low-PUFA [0.3 and 0.6% of total lipids as docosahexaenoic acid (DHA) and arachidonic acid (AA), respectively], or a high-PUFA (5 and 11% of total lipids as DHA and AA, respectively) parenteral solution. Hepatic oxidative capacity and carnitine palmitoyltransferase (CPT) mRNA and activity in the presence or absence of malonyl-CoA were determined after 6 d. Oxidation of [1-¹⁴C]-palmitate or [1-¹⁴C]-glucose was similar in liver homogenates isolated from preterm and term pigs receiving the control solution. Oxidative capacity for either substrate did not differ with parenteral solution in preterm pigs, whereas in term pigs, glucose oxidation was 64% greater when the high-PUFA solution was administered relative to the control (P < 0.05). In preterm pigs, CPT I mRNA determined after 6 d of parenteral feeding were 1.5-fold greater (P < 0.05) than newborn estimates irrespective of solution administered, whereas CPT I mRNA were only greater for term pigs receiving the low- and high-PUFA solutions (66 and 115%, respectively; P < 0.05) relative to newborn estimates. Malonyl-CoA–sensitive CPT activity did not differ between preterm and term pigs or parenteral solution. Postnatal adaptations demonstrated by parenterally fed term neonates are present following preterm birth and are not improved by the provision of DHA and AA to parenteral solutions.

Postprandial Cysteine/Cystine Redox Potential in Human Plasma Varies with Meal Content of Sulfur Amino Acids [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Fri, 19 Mar 2010 09:01:14 PDT

Few data are available on plasma redox responses to sulfur amino acid (SAA) loads. In this study, we had 2 aims: to determine whether the SAA content of a meal affected postprandial plasma cysteine (Cys), cystine (CySS), or redox potential (E_hCySS) in humans and whether SAA intake level (adequate or inadequate) in the days preceding the meal challenge affected these postprandial levels. Eight healthy individuals aged 18–36 y were equilibrated for 3 d to adequate SAA, fed chemically defined meals without SAA for 5 d (inadequate SAA) and then fed isoenergetic, isonitrogenous meals with adequate SAA for 5 d. On the first and last days with the chemically defined meals, a morning meal containing 60% of the daily food intake was given, and plasma Cys, CySS, and E_hCySS were determined over an 8-h postprandial time course. Following equilibration to adequate intake, provision of the meal with SAA resulted in increased plasma Cys and CySS concentrations and more reduced plasma E_hCySS compared with the postprandial values following the same meal without SAA. Equilibration to inadequate SAA intake for the days preceding the meal challenge did not affect this response. The magnitude of the difference in postprandial plasma E_hCySS (10 mV) due to meal content of SAA was comparable to those which alter physiologic signaling and/or are associated with disease risk. Consequently, the SAA content of meals could affect physiologic signaling and associated disease mechanisms in the postprandial period by changes in Cys, CySS, or E_hCySS.

Neonatal Administration of Isoflavones Attenuates Deterioration of Bone Tissue in Female but Not Male Mice [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Kaludjerovic, J., Ward, W. E. — Fri, 19 Mar 2010 09:01:14 PDT

Neonatal exposure to soy isoflavones at levels similar to that of infants fed soy protein formula resulted in higher bone mineral density (BMD), improved bone structure, and greater bone strength at young adulthood in female CD-1 mice (1,2). Our objective in this study was to determine whether these improvements in bone quantity and quality at 4 mo of age provide protection against the deterioration of bone tissue that occurs after a decline in endogenous sex steroid production. Male and female CD-1 mice (n = 8–18 pups per group per gender) were randomized to subcutaneous injections of corn oil [negative control (CON)], daidzein + genistein (DG; 7 mg · kg body weight^–1 · d^–1), or diethylstilbestrol [(DES); positive control, 2 mg · kg body weight^–1 · d^–1) from postnatal d 1 to 5. At 4 mo of age, mice were ovariectomized (females) or orchidectomized (males) and studied to 8 mo of age. Females treated with DG had higher (P < 0.05) femur and vertebral bone mineral content (BMC) and BMD compared with the CON group. Microstructural analysis revealed that improvements in BMD induced by DG and DES were coupled with greater trabecular thickness at the lumbar spine. Importantly, structural improvements resulted in bones that were more resistant to fracture, as the peak load of the femoral midpoint and lumbar vertebra 2 were higher (P < 0.05) with DG compared with CON. Effects in males were not significant. In conclusion, short-term neonatal exposure to isoflavones provides protection against the deterioration of bone tissue in females but not males after a decline of endogenous sex steroid production.

Predicted Apparent Digestion of Energy-Yielding Nutrients Differs between the Upper and Lower Digestive Tracts in Rats and Humans [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Coles, L. T., Moughan, P. J., Awati, A., Darragh, A. J., Zou, M. L. — Fri, 19 Feb 2010 09:01:12 PST

The apparent digestibility of energy-yielding nutrients (carbohydrate, protein, and fat) was predicted in the human upper digestive tract and large bowel separately for 4 diverse diets containing either a single dietary fiber source [wheat bran and pectin (PE) diets] or mixed fiber sources [low-fiber (LF) and high-fiber (HF) diets). A human balance study was undertaken to determine fecal energy and nutrient excretion and a rat model was used to predict human ileal energy and nutrient excretion. Total tract energy digestibility ranged from 92 (HF diet) to 96% (PE diet and LF diet), while at the ileal level it ranged from 79 to 86% for the HF diet to the LF diet. The predicted upper-tract digestion of starch, sugars, and fat was high, with ileal digestibilities exceeding 90% for all diets. Nonstarch polysaccharides were poorly digested in the upper tract for all diets except in the PE diet. The daily quantity of protein excreted at the ileal level was between 2 (HF diet) and 5 (PE diet) times higher than that at the fecal level. The large differences between fecal and ileal nutrient loss highlight that fecal digestibility data alone provide incomplete information on nutrient loss. There is a need to be able to routinely determine the uptake of energy in the upper and lower digestive tracts separately.

Dietary Phosphate Restriction Decreases Stem Cell Proliferation and Subsequent Growth Potential in Neonatal Pigs [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Fri, 19 Feb 2010 09:01:12 PST

Although mesenchymal stem cells (MSC) and satellite cells are essential for postnatal muscle and bone development and phosphate (PO₄) restriction reduces both muscle and skeletal tissue growth, no research to our knowledge has investigated the possible mechanism by which this mineral may affect early cell programming. Twenty piglets obtained at 1 d of age (1.8 ± 0.3 kg) received either a PO₄-adequate diet or a 25% less PO₄-available diet over a 15-d trial. Feed intake and body weight were recorded daily and blood samples collected every 5 d. After 15 d, pigs were given an intraperitoneal injection of bromodeoxyuridine 4 h prior to tissue collection. As expected, PO₄ deficiency resulted in reduced growth (P < 0.05), feed conversion efficiency (P < 0.05), and bone mineral content (P < 0.05), as well as lower plasma concentrations of both PO₄ (P < 0.01) and parathyroid hormone (P < 0.05). In addition to these classical indicators of PO₄ deficiency, there was also reduced proliferation of both MSC (P < 0.01) and satellite cells (P < 0.05) in vivo. The expression of osteocalcin mRNA in bone marrow was also 2-fold greater (P < 0.01) within the PO₄-adequate treatment group. These data indicate that in addition to reductions in muscle and bone growth, dietary PO₄ affects proliferation of tissue-specific stem cells in vivo. Nutritional programming of tissue-specific stem cells by dietary PO₄ may have profound implications for life-long growth potential.

Dietary Supplementation with Lactobacilli and Bifidobacteria Is Well Tolerated and Not Associated with Adverse Events during Late Pregnancy and Early Infancy [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Fri, 19 Feb 2010 09:01:12 PST

Lactic acid bacteria and bifidobacteria are increasingly being administered to pregnant women and infants with the intention of improving health. Although these organisms have a long record of safe use, it is important to identify any adverse effects in potentially vulnerable populations. In a randomized, double-blinded, placebo-controlled trial, we evaluated the safety of a bacterial dietary supplement for the prevention of atopy in infants. Two strains of lactobacilli (Lactobacillus salivarius CUL61 and Lactobacillus paracasei CUL08) and bifidobacteria (Bifidobacterium animalis subsp. lactis CUL34 and Bifidobacterium bifidum CUL20) with a total of 1 x 10¹⁰ colony-forming units were administered daily to women during the last month of pregnancy and to infants aged 0–6 mo. Adverse events (AE) were classified according to WHO International Statistical Classification of Diseases criteria. Common symptoms were recorded by regular questionnaires. Baseline characteristics of 220 mother-infant dyads in the treatment and 234 in the placebo group were similar. Compliance with the trial interventions, loss to follow-up, symptoms, drug usage, infant growth, method of feeding, visits to the doctor, and mothers' assessment of infant health were similar in the 2 groups. Fifteen (6.8%) mothers and 73 (33.2%) infants in the treatment group and 21 (9.0%) mothers and 75 (32.1%) infants in the placebo group reported AE (P = 0.49 and P = 0.84, respectively). Severe AE occurred in 18 mothers and 63 infants with a similar frequency in each group. None of the AE were attributed to the intervention. Our findings support the safe use of this consortium of organisms during pregnancy and early infancy.

Multidrug Resistance Proteins Restrain the Intestinal Absorption of trans-Resveratrol in Rats [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Juan, M. E., Gonzalez-Pons, E., Planas, J. M. — Fri, 19 Feb 2010 09:01:12 PST

trans-Resveratrol, a natural antioxidant, has been described as a nutraceutic compound with important beneficial effects on health, but its low oral bioavailability hinders its therapeutic activity. Here, we studied the mechanisms of apical transport of trans-resveratrol in enterocytes and the role of ATP-binding cassette (ABC) transporters in the secretion of resveratrol glucuronide and sulfate resulting from the rapid intracellular metabolism. An intestinal perfusion method with recirculation in vivo was used in rats. Jejunal loops were perfused with increasing concentrations of trans-resveratrol and results showed that its uptake occurs by simple diffusion without the participation of a mediated transport. The apparent diffusion constant was 8.1 ± 0.3 µL/(5 min·mg dry weight). The glycoprotein-P (Pgp, ABCB1), multidrug resistance-associated protein 2 (MRP2, ABCC2), and breast cancer resistance protein (BCRP, ABCG2) located in the apical membrane of enterocytes were investigated using specific inhibitors. The Pgp inhibitors verapamil (5 µmol/L) and cyclosporin A (5 µmol/L) did not affect the efflux of trans-resveratrol and its conjugates. The MRP2 inhibitors probenecid (2 mmol/L) and MK571 (10 µmol/L) reduced the efflux of glucuronide by 61 and 55%, respectively, and of sulfate by 43 and 28%, respectively. The BCRP inhibitor Ko143 (0.5 µmol/L) decreased the secretion of glucuronide by 64% and of sulfate by 46%. Our experiments identify MRP2 and BCRP as the 2 apical transporters involved in the efflux of resveratrol conjugates.

Isoleucine Prevents the Accumulation of Tissue Triglycerides and Upregulates the Expression of PPAR{alpha} and Uncoupling Protein in Diet-Induced Obese Mice [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Nishimura, J., Masaki, T., Arakawa, M., Seike, M., Yoshimatsu, H. — Fri, 19 Feb 2010 09:01:12 PST

In this study, we investigated the effects of the branched-chain amino acid l-isoleucine (Ile) on both obesity and glucose/fat homeostasis in mice that were fed a high-fat (45% energy) diet. The mice were divided into different treatment groups and given a high-fat diet for 6 wk. During the last 4 wk, Ile was dissolved and added to the drinking water to a final concentration of 2.5%. The control mice received vehicle alone. The mice in the Ile group had an almost 6% lower body weight gain and 49% less epididymal white adipose tissue (WAT) mass with the control group (P < 0.05). The hepatic and skeletal muscle triglyceride (TG) concentrations and degree of hyperinsulinemia in the Ile group mice were also lower than the control group by 38, 47, and 39%, respectively (P < 0.05). The WAT leptin concentration was also lower, whereas that of adiponectin was higher, in the Ile group compared with the control group (P < 0.05). The hepatic levels of protein CD36/fatty acid translocase, PPAR, and uncoupling protein (UCP) 2 and the levels of UCP3 in skeletal muscle were all greater in the Ile group than in the control mice (P < 0.05). These results demonstrate that the liver and muscle TG concentrations are both lowered by Ile treatment. In addition, the PPAR and UCP expression levels in the mouse tissues were greater in the Ile group compared with the controls. Our current data thus suggest that supplementation with Ile might be useful in the treatment of metabolic syndrome.

Elevated Circulating LDL Phenol Levels in Men Who Consumed Virgin Rather Than Refined Olive Oil Are Associated with Less Oxidation of Plasma LDL [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Fri, 19 Feb 2010 09:01:12 PST

In human LDL, the bioactivity of olive oil phenols is determined by the in vivo disposition of the biological metabolites of these compounds. Here, we examined how the ingestion of 2 similar olive oils affected the content of the metabolic forms of olive oil phenols in LDL in men. The oils differed in phenol concentrations as follows: high (629 mg/L) for virgin olive oil (VOO) and null (0 mg/L) for refined olive oil (ROO). The study population consisted of a subsample from the EUROLIVE study and a randomized controlled, crossover design was used. Intervention periods lasted 3 wk and were preceded by a 2-wk washout period. The levels of LDL hydroxytyrosol monosulfate and homovanillic acid sulfate, but not of tyrosol sulfate, increased after VOO ingestion (P < 0.05), whereas the concentrations of circulating oxidation markers, including oxidized LDL (oxLDL), conjugated dienes, and hydroxy fatty acids, decreased (P < 0.05). The levels of LDL phenols and oxidation markers were not affected by ROO consumption. The relative increase in the 3 LDL phenols was greater when men consumed VOO than when they consumed ROO (P < 0.05), as was the relative decrease in plasma oxLDL (P = 0.001) and hydroxy fatty acids (P < 0.001). Plasma oxLDL concentrations were negatively correlated with the LDL phenol levels (r = –0.296; P = 0.013). Phenols in LDL were not associated with other oxidation markers. In summary, the phenol concentration of olive oil modulates the phenolic metabolite content in LDL after sustained, daily consumption. The inverse relationship of these metabolites with the degree of LDL oxidation supports the in vivo antioxidant role of olive oil phenolics compounds.

Changes in Intestinal Bifidobacteria Levels Are Associated with the Inflammatory Response in Magnesium-Deficient Mice [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Fri, 19 Feb 2010 09:01:12 PST

Magnesium (Mg) deficiency is a common nutritional disorder that is linked to an inflammatory state characterized by increased plasma acute phase protein and proinflammatory cytokine concentrations. Recent studies have shown that changes in the composition of gut microbiota composition participate in systemic inflammation. In this study, therefore, we assessed the potential role of gut microbiota in intestinal and systemic inflammation associated with Mg deficiency in mice. For this purpose, mice were fed a control or Mg-deficient diet (500 mg vs. 70 mg Mg/kg) for 4 or 21 d. Compared with the mice fed the control diet, mice fed the Mg-deficient diet for 4 d had a lower gut bifidobacteria content (–1.5 log), a 36–50% lower mRNA content of factors controlling gut barrier function in the ileum (zonula occludens-1, occludin, proglucagon), and a higher mRNA content (by ~2-fold) in the liver and/or intestine of tumor necrosis factor-, interleukin-6, CCAAT/enhancer binding protein homologous protein, and activating transcription factor 4, reflecting inflammatory and cellular stress. In contrast, mice fed the Mg-deficient diet for 21 d had a higher cecal bifidobacteria content compared with the control group, a phenomenon accompanied by restoration of the intestinal barrier and the absence of inflammation. In conclusion, we show that Mg deficiency, independently of any other changes in nutrient intake, modulates the concentration of bifidobacteria in the gut, a phenomenon that may time-dependently affect inflammation and metabolic disorders in mice.

The Polyunsaturated Fatty Acid Composition of Hepatic and Plasma Lipids Differ by Both Sex and Dietary Fat Intake in Rats [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Childs, C. E., Romeu-Nadal, M., Burdge, G. C., Calder, P. C. — Wed, 20 Jan 2010 09:03:14 PST

In rats and humans, females have higher liver and/or plasma docosahexaenoic acid (DHA) content than males. We hypothesized that the effect of variation in total fat or essential fatty acid intakes on liver and plasma fatty acid composition would differ between sexes. Rats were fed a low-fat soybean oil (LFS), high-fat soybean oil (HFS), or high-fat linseed oil (HFL) diet for 20 d. There were significant sex differences in LFS rats in proportions of (n-3) and (n-6) fatty acids in plasma and liver contingent on lipid class. Significant diet x sex interactions were observed for eicosapentaenoic acid (EPA), DHA, and arachidonic acid (AA) status. HFL females had a higher proportion of EPA in plasma and liver phosphatidylcholine (PC), DHA in liver triacylglycerol (TAG), and AA in plasma PC than HFS and LFS females. These findings show that the effect of varying dietary fat intake on (n-3) and (n-6) long-chain PUFA (LCPUFA) status is modified by sex. Liver phospholipid and TAG fatty acid product:substrate ratios suggested greater 6 desaturase (6D) activity in females than in males. The HFL diet induced higher 6D mRNA expression compared with the LFS or HFS diets and HFL females had 10% higher expression of 6D mRNA than HFL males. Together, these findings show that sex is an important determinant of the effect of variations in fat and fatty acid intake on LCPUFA status, which may have implications for recommendations for fat and fatty acid intake in humans.

Sildenafil Citrate Treatment Enhances Amino Acid Availability in the Conceptus and Fetal Growth in an Ovine Model of Intrauterine Growth Restriction [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Satterfield, M. C., Bazer, F. W., Spencer, T. E., Wu, G. — Wed, 20 Jan 2010 09:03:14 PST

Adequate placental blood flow is essential for the optimal delivery of nutrients from mother to fetus for conceptus growth. Restricted fetal development results from pathophysiological and environmental factors that alter utero-placental blood flow, placental function, and, therefore, nutrient availability in the fetus. To test this hypothesis, 0, 75, or 150 mg/d sildenafil citrate (Viagra) was administered subcutaneously from d 28 to 115 of gestation to either nutrient-restricted [50% of NRC requirements) or adequately-fed ewes (100% of NRC requirements). On d 115, maternal, fetal, and placental tissues and fluids were collected. Concentrations of total amino acids and polyamines in uterine venous and arterial sera, amniotic and allantoic fluids, and fetal umbilical venous serum were lower (P < 0.05) in nutrient-restricted ewes than in adequately fed ewes, as were the ratios of total amino acids in fetal umbilical venous serum to uterine arterial serum. Sildenafil citrate dose-dependently increased (P < 0.05) total amino acids and polyamines in amniotic fluid, allantoic fluid, and fetal serum without affecting values in maternal serum. Fetal weight was lower (P < 0.05) in nutrient-restricted ewes on d 115. Sildenafil citrate treatment dose-dependently increased (P < 0.05) fetal weight in both nutrient-restricted and adequately fed ewes. This study supports the hypothesis that long-term sildenafil citrate treatment enhances fetal growth, at least in part, by increasing the availability of amino acids in the conceptus. These findings may lead to the clinical use of sildenafil citrate in human pregnancies suspected to be at risk for intrauterine fetal growth retardation.

Nondairy Creamer, but Not Milk, Delays the Appearance of Coffee Phenolic Acid Equivalents in Human Plasma [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Wed, 20 Jan 2010 09:03:14 PST

Chlorogenic acids (CGA) are antioxidants found in coffee. They are becoming of interest for their health-promoting effects, but bioavailability in humans is not well understood. We hypothesized that adding whole milk or sugar and nondairy creamer to instant coffee might modulate the bioavailability of coffee phenolics. Nine healthy participants were asked to randomly drink, in a crossover design, instant coffee (Coffee); instant coffee and 10% whole milk (Milk); or instant coffee, sugar, and nondairy creamer already premixed (Sugar/NDC). All 3 treatments provided the same amount of total CGA (332 mg). Blood was collected for 12 h after ingestion and plasma samples treated using a liquid-liquid extraction method that included a full enzymatic cleavage to hydrolyze all CGA and conjugates into phenolic acid equivalents. Hence, we focused our liquid chromatography-Electrospray ionization-tandem MS detection and quantification on caffeic acid (CA), ferulic acid (FA), and isoferulic acid (iFA) equivalents. Compared with a regular black instant coffee, the addition of milk did not significantly alter the area under the curve (AUC), maximum plasma concentration (C_max), or the time needed to reach C_max (T_max). The C_max of CA and iFA were significantly lower and the T_max of FA and iFA significantly longer for the Sugar/NDC group than for the Coffee group. However, the AUC did not significantly differ. As a conclusion, adding whole milk did not alter the overall bioavailability of coffee phenolic acids, whereas sugar and nondairy creamer affected the T_max and C_max but not the appearance of coffee phenolics in plasma.

Stimulation of Muscle Protein Synthesis by Prolonged Parenteral Infusion of Leucine Is Dependent on Amino Acid Availability in Neonatal Pigs [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Wed, 20 Jan 2010 09:03:14 PST

The postprandial rise in amino acids, particularly leucine, stimulates muscle protein synthesis in neonates. Previously, we showed that a 1-h infusion of leucine increased protein synthesis, but this response was not sustained for 2 h unless the leucine-induced decrease in amino acids was prevented. To determine whether a parenteral leucine infusion can stimulate protein synthesis for a more prolonged, clinically relevant period if baseline amino acid concentrations are maintained, overnight food-deprived neonatal pigs were infused for 24 h with saline, leucine (400 µmol·kg^–1· h^–1), or leucine with replacement amino acids. Amino acid replacement prevented the leucine-induced decrease in amino acids. Muscle protein synthesis was increased by leucine but only when other amino acids were supplied to maintain euaminoacidemia. Leucine did not affect activators of mammalian target of rapamycin (mTOR), i.e. protein kinase B, AMP-activated protein kinase, tuberous sclerosis complex 2, or eukaryotic elongation factor 2. There was no effect of treatment on the association of mTOR with regulatory associated protein of mammalian target of rapamycin (raptor), G-protein β subunit-like protein, or rictor or the phosphorylation of raptor or proline-rich Akt substrate of 40 kDa. Phosphorylation of mTOR and its downstream targets, eukaryotic initiation factor (eIF) 4E binding protein and ribosomal protein S6 kinase, and the eIF4E · eIF4G association were increased and eIF2 phosphorylation was reduced by leucine and was not further altered by correcting for the leucine-induced hypoaminoacidemia. Thus, prolonged parenteral infusion of leucine activates mTOR and its downstream targets in neonatal skeletal muscle, but the stimulation of protein synthesis also is dependent upon amino acid availability.

Age and Dietary Iron Affect Expression of Genes Involved in Iron Acquisition and Homeostasis in Young Pigs [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Hansen, S. L., Trakooljul, N., Spears, J. W., Liu, H.-C. — Wed, 20 Jan 2010 09:03:14 PST

To investigate the effects of dietary iron (Fe) and age on Fe metabolism, we used 36 weaned barrows in a 2 x 3 design with 2 concentrations of dietary Fe [97 (control) and 797 (high Fe) mg Fe/kg dry matter] and 3 time points of tissue collection (after 21, 42, or 63 d on diets). Pigs were weighed and bled on d 0, 20, 41, and 62. High Fe reduced feed efficiency but did not affect pig weight gain. Blood hemoglobin concentrations and Fe concentrations of liver, intestine, and heart were increased by high dietary Fe on all days. Concentrations of liver and heart Fe increased with age. As determined by quantitative real-time PCR, hepatic expression of hepcidin (HAMP) in pigs given the high-Fe diet was 6.25-fold that of control pigs. In the intestine, relative mRNA levels of ferroportin, divalent metal transporter 1, and transferrin receptor were downregulated by high Fe. Expression of an alternative route of Fe absorption, solute carrier family 39 member 14 (SLC39A14), was downregulated in the intestine of pigs fed high dietary Fe. Additionally, duodenal mRNA level of certain genes including scavenger receptor class A, member 5, and frataxin decreased with age of the animal. Our findings indicate new roles in Fe metabolism for several mineral metabolism-associated genes and that some of these genes, such as SLC39A14, may be regulated in response to dietary Fe in pigs. Additionally, the expression of some genes examined in this study was affected by age, suggesting age dependency of Fe metabolism in pigs.

Serum Lipid and Blood Pressure Responses to Quercetin Vary in Overweight Patients by Apolipoprotein E Genotype [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Egert, S., Boesch-Saadatmandi, C., Wolffram, S., Rimbach, G., Muller, M. J. — Wed, 20 Jan 2010 09:03:14 PST

Our objective was to examine the effect of a quercetin supplementation on blood pressure, lipid metabolism, markers of oxidative stress, inflammation, and body composition in an at-risk population of 93 overweight-obese volunteers aged 25–65 y with metabolic syndrome traits in relation to apolipoprotein (apo) E genotype. Participants were randomized to receive 150 mg/d quercetin in a double-blinded, placebo-controlled, crossover trial with 6-wk treatment periods separated by a 5-wk washout period. Retrospectively, 5 apoE genotype variants were found (2/3, n = 3; 3/3, n = 60; 3/4, n = 23; 2/4, n = 4; and 4/4, n = 3). Participants were classified into the following 3 apoE phenotypes: apoE2 (n = 3), apoE3 (n = 60), and apoE4 (n = 26). Data were analyzed for apoE3 and apoE4 subgroups. Quercetin decreased systolic blood pressure by 3.4 mm Hg (P < 0.01) in the apoE3 group, whereas no significant effect was observed in the apoE4 group. Quercetin decreased serum HDL cholesterol (P < 0.01) and apoA1 (P < 0.01) and increased the LDL:HDL cholesterol ratio (P < 0.05) in the apoE4 subgroup, whereas the apoE3 subgroup had no significant changes in these variables. Quercetin significantly decreased plasma oxidized LDL and tumor necrosis factor- in the apoE3 and apoE4 groups, whereas no significant inter-group differences were found. Serum C-reactive protein and nutritional status (body weight, waist circumference, fat mass, fat-free mass) were unaffected compared with placebo. In conclusion, quercetin exhibited blood pressure-lowering effects in overweight-obese carriers of the apo 3/3 genotype but not in carriers of the 4 allele. Furthermore, quercetin supplementation resulted in a reduction in HDL cholesterol and apoA1 in apo 4 carriers.

Nutritional Stimulation of Milk Protein Yield of Cows Is Associated with Changes in Phosphorylation of Mammary Eukaryotic Initiation Factor 2 and Ribosomal S6 Kinase 1 [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Toerien, C. A., Trout, D. R., Cant, J. P. — Wed, 20 Jan 2010 09:03:14 PST

Production of protein by the lactating mammary gland is stimulated by intake of dietary energy and protein. Mass-action effects of essential amino acids (EAA) cannot explain all of the nutritional response. Protein synthesis in tissues of growing animals is regulated by nutrients through the mammalian target of rapamycin (mTOR) and integrated stress response (ISR) networks. To explore if nutrients signal through the mTOR and ISR networks in the mammary gland in vivo, lactating cows were feed-deprived for 22 h and then infused i.v. for 9 h with EAA+ glucose (Glc), Glc only, l-Met+l-Lys, l-His, or l-Leu. Milk protein yield was increased 33 and 27% by EAA+Glc and Glc infusions, respectively. Infusions of Met+Lys and His generated 35 and 41%, respectively, of the EAA+Glc response. Infusion of EAA+Glc reduced phosphorylation of the ISR target, eukaryotic initiation factor(eIF) 2, in mammary tissue and increased phosphorylation of the mTOR targets, ribosomal S6 kinase 1 (S6K1) and S6. Both responses are stimulatory to protein synthesis. Glucose did not significantly increase mammary S6K1 phosphorylation but reduced eIF2 phosphorylation by 62%, which implicates the ISR network in the stimulation of milk protein yield. In contrast, the EAA infusions increased (P < 0.05) or tended to increase (P < 0.1) mammary mTOR activity and only His, like Glc, decreased eIF2 phosphorylation by 62%. Despite activation of these protein synthesis signals to between 83 and 127% of the EAA+Glc response, EAA infusions produced less than one-half of the milk protein yield response generated by EAA+Glc, indicating that ISR and mTOR networks exert only a portion of the control over protein yield.

Acute Ingestion of Long-Chain (n-3) Polyunsaturated Fatty Acids Decreases Fibrinolysis in Men with Metabolic Syndrome [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Montegaard, C., Tulk, H. M. F., Lauritzen, L., Tholstrup, T., Robinson, L. E. — Fri, 18 Dec 2009 09:01:33 PST

Individuals with metabolic syndrome (MetS) often have elevated plasma plasminogen activator inhibitor-1 (PAI-1) and tissue plasminogen activator (t-PA), contributing to an increased risk of cardiovascular disease. PAI-1 and t-PA may be affected by chronic (n-3) long-chain PUFA [(n-3)LCPUFA] supplementation; however, the acute impact of fat ingestion on these risk factors has not been established. Our objective was to investigate the acute effect of (n-3)LCPUFA on plasma PAI-1, t-PA, and platelet aggregation. We conducted a randomized crossover study in which men (n = 8, ≥45 y) with MetS consumed water or a high-saturated fat beverage (1 g fat/kg body weight) with either a high or low content of (n-3)LCPUFA. Blood samples were collected over 8 h to measure triacylglycerol (TAG), PAI-1, t-PA, and platelet aggregation. Both fat loads resulted in a significant increase in whole blood TAG concentration, plasma PAI-1 and t-PA concentrations, and PAI-1 activity, as well as a significant decrease in t-PA activity during the postprandial period. Interestingly, PAI-1 concentration and activity increased more following the high (n-3)LCPUFA compared with the low (n-3)LCPUFA beverage (P < 0.05). Furthermore, the high (n-3)LCPUFA beverage resulted in a lower t-PA activity (P < 0.05), whereas the effects of the 2 fat loads on the plasma t-PA concentration and platelet aggregation did not differ. Overall, acute intake of a high (n-3)LCPUFA beverage shifted the balance between plasma PAI-1 and t-PA, which might indicate a lower capacity for fibrinolysis.

Oral Glutamine Protects against Acute Doxorubicin-Induced Cardiotoxicity of Tumor-Bearing Rats [Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions]

Todorova, V. K., Kaufmann, Y., Hennings, L., Klimberg, V. S. — Fri, 18 Dec 2009 09:01:33 PST

Doxorubicin (DOX), a widely used anticancer drug, has a dose-dependent cardiotoxicity, attributed mainly to free radical formation. The cardiomyocyte oxidative stress occurs rapidly after DOX treatment, resulting in harmful modifications to proteins, lipids, and DNA. Previous data showed that oral l-glutamine (Gln) prevented cardiac lipid peroxidation and maintained normal cardiac glutathione (GSH) levels in DOX-treated rats. Our aim in this study was to examine the effect of Gln on DOX-induced cardiac oxidative stress in a tumor-bearing host. Female Fisher344 rats with implanted MatBIII mammary tumors were randomized into 2 groups: a Gln group that received l-Gln (1 g·kg^–1·d^–1) (n = 10) via a Gln-enriched diet and/or gavage with 50% Gln suspension during the whole experiment and a control group that was fed the same diet formulation without Gln and/or were gavaged with water. All rats received a single injection of 12 mg/kg DOX and were killed 3 d later. GSH levels of hearts, livers, tumors, and blood, as well as cardiac histological alterations, lipid peroxidation, peroxinitrite levels, and caspase-3 activation were determined. Cardiac physiologic alterations were assessed by ultrasound imaging before and 3 d after DOX administration. The Gln supplementation resulted in lower cardiac lipid peroxidation and peroxintrite levels and elevated cardiac catalase enzyme activity and GSH compared with the controls, without affecting those of the tumors. DOX-induced alterations of the echocardiographic parameters were significantly reduced in the Gln-supplemented rats. These data indicate that Gln is able to reduce the oxidative damage of cardiomyocytes that occurs soon after DOX administration and thus protects the heart of a tumor-bearing host from DOX-induced cardiomyopathy.