bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional dissection of the interactions of stonin 2 with the adaptor complex AP-2 and synaptotagmin
Authors: Walther Kristin , Diril M. Kasim , Jung Nadja , Haucke Volker
Published: January 2004

Synaptic vesicle recycling is in part mediated by clathrin-mediated endocytosis. This process involves the coordinated assembly of clathrin and adaptor proteins and the concomitant selection of cargo proteins. Here, we demonstrate that the endocytotic protein stonin 2 localizes to axonal vesicle clusters through its μ-homology domain. Interaction of this domain with synaptotagmin I is sufficient to recruit stonin 2 to the plasmalemma. The N-terminal domain of stonin 2 harbors multiple AP-2-interaction motifs that bind to the clathrin adaptor complex AP-2. These motifs with the consensus sequence WVxF are capable of binding to the α-adaptin ear domain and to μ2. Mutation of the tyrosine motif-binding pocket of μ2 abolishes recognition of the WVxF peptide, suggesting that association with stonin 2 renders AP-2 incompetent to sort tyrosine motif-containing cargo proteins. We hypothesize that stonin 2 may function as an AP-2-dependent sorting adaptor for synaptic vesicle recycling.
The
Arabidopsis
double-stranded RNA-binding protein HYL1 plays a role in microRNA-mediated gene regulation
Authors: Han Meng-Hsuan , Goud Saiprasad , Song Liang , Fedoroff Nina
Published: January 2004

The
Arabidopsis HYL1
gene encodes a nuclear double-stranded RNA-binding protein. A knockout mutation of the
hyl1
gene is recessive and pleiotropic, causing developmental abnormalities, increasing sensitivity to abscisic acid, and reducing sensitivity to auxin and cytokinin. We report that levels of several microRNAs (miRNAs; miR159, -167, and -171) are reduced in homozygous mutant plants, and levels of two of three tested target mRNAs are elevated. Conversely, the miRNA levels are elevated in plants expressing a
HYL1
cDNA from a strong promoter, and the corresponding target RNAs are reduced. These changes result from alterations in the stability of the target RNAs. However, double-stranded RNA-induced posttranscriptional gene silencing is unaffected by the
hyl1
mutation. One-third to one-half of the cellular HYL1 protein is in a macromolecular complex, and a GFP-HYL1 fusion protein is found predominantly in the nucleus, although it is observed in both nucleus and cytoplasm in some cells. Within nuclei, HYL1 is associated with subnuclear bodies and ring-like structures. These observations provide evidence that the HYL1 protein is part of a nuclear macromolecular complex that is involved in miRNA-mediated gene regulation. Because
hyl1
mutants show marked abnormalities in hormone responses, these results further suggest that miRNA-mediated changes in mRNA stability play a vital role in plant hormone signaling.
A feedback mechanism regulates monoallelic odorant receptor expression
Authors: Lewcock Joseph W. , Reed Randall R.
Published: January 2004

In olfactory neurons, expression of a single odorant receptor (OR) from a repertoire of >1,000 genes is required for odor coding and axonal targeting. Here, we demonstrate a role for OR protein as an essential regulator in the establishment of monoallelic OR expression. An OR-promoter-driven reporter expresses in a receptor-like pattern but, unlike a native OR, is coexpressed with an additional OR allele. Expression of a functional OR from the identical promoter eliminates expression of other OR alleles. The presence of an untranslatable OR coding sequence in the mRNA is insufficient to exclude expression of a second OR. Together, these data identify the OR protein as a critical element in a feedback pathway that regulates OR selection.
Short-chain fatty acids stimulate leptin production in adipocytes through the G protein-coupled receptor GPR41
Authors: Xiong Yumei , Miyamoto Norimasa , Shibata Kenji , Valasek Mark A. , Motoike Toshiyuki , Kedzierski Rafal M. , Yanagisawa Masashi
Published: January 2004

Leptin is an adipose-derived hormone that regulates a wide variety of physiological processes, including feeding behavior, metabolic rate, sympathetic nerve activity, reproduction, and immune response. Circulating leptin levels are tightly regulated according to energy homeostasis
in vivo
. Although mechanisms for the regulation of leptin production in adipocytes are not well understood, G protein-coupled receptors may play an important role in this adipocyte function. Here we report that C2–C6 short-chain fatty acids, ligands of an orphan G protein-coupled receptor GPR41, stimulate leptin expression in both a mouse adipocyte cell line and mouse adipose tissue in primary culture. Acute oral administration of propionate increases circulating leptin levels in mice. The concentrations of short-chain fatty acids required to stimulate leptin production are within physiological ranges, suggesting the relevance of this pathway
in vivo
.
Specificity determinants and diversification of the
Brassica
self-incompatibility pollen ligand
Authors: Chookajorn Thanat , Kachroo Aardra , Ripoll Daniel R. , Clark Andrew G. , Nasrallah June B.
Published: January 2004

Self-incompatibility in crucifers is effected by allele-specific interactions between the highly polymorphic stigmatic
S
locus receptor kinase (SRK) and its pollen ligand, the
S
locus cysteine-rich protein (SCR). Here we show that specificity in SCR function is determined by four contiguous amino acids in one variant, indicating that the minimum sequence requirement for gaining a new specificity can be low. We also provide evidence for an extraordinarily high degree of evolutionary flexibility in SCR, whereby SCR can tolerate extensive amino acid changes within the limits of maintaining the same predicted overall structure. This remarkable adaptability suggests a hypothesis for generation of new self-incompatibility specificities by gradual modification of SRK-SCR affinities and, more generally, for functional specialization within families of homologous ligands and receptors.
Energy balance of pregnant diabetic rats
Authors: Yamada Ruth , Griggio Mauro A. , Luz Jacqueline
Published: January 2004

Pregnancy and diabetes lead to metabolic alterations in the energy balance that may not be completely independent. The objective of the present study was to look at the alterations induced by type 1 diabetes mellitus on the energy balance of pregnant rats and the offspring. Diabetes was induced by streptozotocin injection 15 d before the starting of pregnancy. The rats had their energy balance variables followed for 21 d. Protein, fat and energy content of dams was determined from samples of the carcasses. Pregnancy led to increased energy intake, energy gain and energy expenditure as well as higher gross food efficiency than non-pregnant counterparts. Diabetes increased metabolizable energy intake but not the energy gain of the animals: they had very high energy expenditure, so that diabetes blocked the improvement in gross food efficiency shown during pregnancy. Offspring from diabetic dams were born with lower body weight. Pregnant animals did not present the usual energy storage as seen by lower energy gain of diabetic dams as well as by the lower fat content in the carcasses of pregnant diabetic rats. It is concluded that diabetes impairs the energy variables usually enhanced by pregnancy alone.
Effects of dietary oxysterols on coronary arteries in hyperlipidaemic hamsters
Authors: Meynier Alexandra , Lherminier Jeanine , Demaison-Meloche Joelle , Ginies Christian , Grandgirard Andre , Demaison Luc
Published: January 2004

The aim of this study was to evaluate the effect of dietary oxysterols on coronary atherosclerosis and vasospasm. Golden Syrian hamsters were fed three diets with different lipid contents for 3 months: (1) a normolipidaemic diet containing 25 g corn oil–fish oil (4:1, w/w)/kg (group Low L); (2) a hyperlipidaemic diet composed of the normolipidaemic diet supplemented with 150 g lard+30 g cholesterol/kg (group High L); (3) a third diet, similar to the hyperlipidaemic diet, in which 4 g cholesterol/kg was replaced by a mixture of oxysterols (group High L+OS). The oxysterol mixture contained (g/kg): 5,6α-epoxycholesterol 211, 5,6β-epoxycholesterol 179, 7α-hydroxycholesterol 67, 7β-hydroxycholesterol (7βOH) 185, 7-ketocholesterol (7 K) 235; and trace amounts of 7-hydroperoxycholesterols (approximately 30 g/kg). Atherosclerosis was evaluated by measuring myocardial Ca, oxysterols and acyl-CoA cholesterol acyl transferase (ACAT) activity; furthermore, coronary reactivity to sodium nitroprusside (5×10-6 m) was measured and the morphology of coronary arteries was visualized by transmission electron microscopy. Coronary spasm was determined by evaluating reactivity to serotonin (5×10-6 m). Feeding the high-lipid diet (group High L) increased the plasma level of 7βOH, 7 K and cholestanetriol. The presence of oxysterols in the diet (group High L+OS) further increased the concentrations of 7βOH and 7 K in the plasma. However, as evidenced by myocardial Ca, ACAT activity and coronary reactivity to sodium nitroprusside, severe atherosclerosis did not develop during the 3-month diet. 7 K was increased in myocardial lipids of groups High L and High L+OS. Electron microscopy did not show the development of atherosclerosis in group High L, whereas vascular wall thickening, endothelial damage and smooth muscle cell proliferation and migration occurred when oxysterols were present in the food. Serotonin (5×10-6 m) induced exacerbated coronary vasoconstriction in group High L that was completely reversed by dietary oxysterols. In conclusion, dietary oxysterols exhibit anti-spasmodic properties, but they cannot be used as agents against excess dietary lipid-induced coronary spasm because of their atherogenic properties.
Eicosapentaenoic acid and docosahexaenoic acid from fish oils: differential associations with lipid responses
Authors: Leigh-Firbank Elizabeth C. , Minihane Anne M. , Leake David S. , Wright John W. , Murphy Margaret C. , Griffin Bruce A. , Williams Christine M.
Published: January 2004

Fish-oil supplementation can reduce circulating triacylglycerol (TG) levels and cardiovascular risk. This study aimed to assess independent associations between changes in platelet eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and fasting and postprandial (PP) lipoprotein concentrations and LDL oxidation status, following fish-oil intervention. Fifty-five mildly hypertriacylglycerolaemic (TG 1·5–4·0 mmol/l) men completed a double-blind placebo controlled cross over study, where individuals consumed 6 g fish oil (3 g EPA+DHA) or 6 g olive oil (placebo)/d for two 6-week intervention periods, with a 12-week wash-out period in between. Fish-oil intervention resulted in a significant increase in the platelet phospholipid EPA (+491 %,P<0·001) and DHA (+44 %,P<0·001) content and a significant decrease in the arachidonic acid (-10 %,P<0·001) and γ-linolenic acid (-24 %,P<0·001) levels. A 30 % increase inex vivoLDL oxidation (P<0·001) was observed. In addition, fish oil resulted in a significant decrease in fasting and PP TG levels (P<0·001), PP non-esterified fatty acid (NEFA) levels, and in the percentage LDL as LDL-3 (P=0·040), and an increase in LDL-cholesterol (P=0·027). In multivariate analysis, changes in platelet phospholipid DHA emerged as being independently associated with the rise in LDL-cholesterol, accounting for 16 % of the variability in this outcome measure (P=0·030). In contrast, increases in platelet EPA were independently associated with the reductions in fasting (P=0·046) and PP TG (P=0·023), and PP NEFA (P=0·015), explaining 15–20 % and 25 % of the variability in response respectively. Increases in platelet EPA+DHA were independently and positively associated with the increase in LDL oxidation (P=0·011). EPA and DHA may have differential effects on plasma lipids in mildly hypertriacylglycerolaemic men.
The immune system as a physiological indicator of marginal copper status?
Authors: Bonham Maxine , O'Connor Jacqueline M. , Hannigan Bernadette M. , Strain J. J.
Published: January 2004

Cu appears to have many important functional roles in the body that apparently relate, among others, to the maintenance of immune function, bone health and haemostasis. Some have suggested a role for long-term marginal Cu deficiency in the aetiology of a number of degenerative diseases. Accurate diagnosis of marginal Cu deficiency, however, has remained elusive despite an increased understanding of the biochemistry of Cu and its physiological roles in the body. Traditional markers of Cu status, such as serum Cu and caeruloplasmin protein concentrations are insensitive to subtle changes in Cu status. Cu-containing enzymes, such as Cu–Zn-superoxide dismutase, cytochromecoxidase and diamine oxidase, may be more reliable but evidence to date is not conclusive. Development of markers sensitive to marginal Cu status is essential before conclusions can be drawn concerning the risks of long-term intake of suboptimal dietary Cu. As Cu appears to be essential for maintenance of immune function, activities of specific immunological markers, altered in Cu deficiency, offer alternatives. This review evaluates a selection of immunological markers that could be considered potentially sensitive markers of marginal Cu status. The indices of immune function reviewed are neutrophil function, interleukin 2 production, blastogenic response to mitogens and lymphocyte subset phenotyping.
Effect of multivitamins in an effervescent preparation on the respiratory burst of peritoneal macrophages in mice
Authors: Jakus Judit , Kriska Tamás , Vanyúr Rozália
Published: January 2004

The effect of regular intake of low doses of an effervescent multivitamin preparation on the free-radical-producing activity of murine peritoneal macrophages under conditions resembling a possible infection was studiedin vitro. Initially, several groups of mice were fed a basal diet and given, for 2 weeks, water without or with supplementation of either α -tocopherol, ascorbic acid, riboflavin or a multivitamin preparation. The supplementation period was followed by a 2-week wash-out time interval during which control and multivitamin groups received deionized water. Macrophage stimulation tests using chemiluminescent spectroscopy were performed at the end of the supplementation and wash-out periods to determine cell counts and their capacity to produce free radicals. Multivitamin supplementation increased the number, and the reactive oxygen species-producing activity, of macrophages. This effect persisted for 2 weeks after higher doses of supplementation were stopped. Multivitamin supplementation lowered the steady-state free radical concentrations of liver and spleen as measured by electron paramagnetic resonance spectroscopy. It also increased the antioxidant reactivity of the same organs, while there was no effect on the free radical concentration and antioxidant capacity of the kidney and brain. When taken regularly, low doses of multivitamin supplementation may have a beneficial effect on the defence mechanisms of the organism.
A modified dot-blot method of protein determination applied in the tannin-protein precipitation assay to facilitate the evaluation of tannin activity in animal feeds
Authors: Hoffmann E. M. , Muetzel S. , Becker K.
Published: January 2004

Tannins have received considerable attention from animal nutritionists as potential agents for modifying ruminal fermentation patterns, or for exploring new feed resources. This group of secondary plant compounds is defined by their ability to form complexes with proteins. A widely accepted method for assaying the biological activity of extracted tannins is the precipitation of bovine serum albumin. The protein carries a radioactive label (125I) to allow direct quantification from the precipitate. Tannin–protein complexes dissolve in sodium dodecylsulfate solution. A dot-blot assay for protein determination, which is based on the reversible binding of a fluorochrome, benzoxanthene yellow, to the protein spots and is not disturbed by the presence of detergents, can replace the radioactive method by a fluorimetric measurement. A novel alternative to the last part of the dot-blot assay is to scan the stained protein spotsin situusing a video camera and computer image analysis. Several filter sets were tested and, within a concentration range of 0·1–2·0 mg protein/ml, each of them yielded results identical to the original method while the time required was only 30 % of the working time consumed by the original procedure. The modified dot-blot assay should be applicable to the evaluation of tannin activity in all shrub and tree foliages considered as animal feed.
Protein and arginine requirements for maintenance and nitrogen gain in four teleosts
Authors: Fournier V. , Gouillou-Coustans M. F. , Métailler R. , Vachot C. , Guedes M. J. , Tulli F. , Oliva-Teles A. , Tibaldit E. , Kaushik S. J.
Published: January 2004

Besides being an indispensable amino acid for protein synthesis, arginine (Arg) is also involved in a number of other physiological functions. Available data on the quantitative requirement for Arg in different teleosts appear to show much variability. So far, there are very limited data on the maintenance requirements of indispensable amino acids (IAA) in fish. In the present study, we compared N and Arg requirements for maintenance and growth of four finfish species: rainbow trout (Oncorhynchus mykiss), turbot (Psetta maxima), gilthead seabream (Sparus aurata) and European seabass (Dicentrarchus labrax). Groups of fish having an initial body weight close to 5–7 g were fed semi-purified diets containing graded levels of N (0 to 8 % DM) and Arg (0 to 3 % DM) over 4 to 6 weeks. For each species, N and Arg requirements for maintenance and for growth were calculated regressing daily N gain against daily N or Arg intakes. N requirement for maintenance was estimated to be 37·8, 127·3, 84·7 and 45·1 mg/kg metabolic body weight per d and 2·3, 2·2, 2·6 and 2·5 g for 1 g N accretion, in rainbow trout, turbot, gilthead seabream and European seabass respectively. The four species studied appear to have very low or no dietary Arg requirements for maintenance. Arg requirement for g N accretion was calculated to be 0·86 g in rainbow trout and between 1·04–1·11 g in the three marine species. Turbot required more N for maintenance than the other three species, possibly explaining its reputedly high overall dietary protein requirement. Data suggest a small but sufficient endogenous Arg synthesis to maintain whole body N balance and differences between freshwater and marine species as regards Arg requirement. It is worth verifying this tendency with other IAA.
Different effects of diets rich in olive oil, rapeseed oil and sunflower-seed oil on postprandial lipid and lipoprotein concentrations and on lipoprotein oxidation susceptibility
Authors: Nielsen Nina S. , Pedersen Anette , Sandström Brittmarie , Marckmann Peter , Høy Carl-Erik
Published: January 2004

Elevated concentrations of fasting and non-fasting triacylglycerol-rich lipoproteins (TRL) as well as oxidative changes of lipoproteins may increase the risk of ischaemic heart disease. To compare the effects of different diets rich in unsaturated fatty acids on the concentrations andin vitrooxidation of fasting and postprandial lipoproteins eighteen males consumed diets enriched with rapeseed oil (RO), olive oil (OO), or sunflower-seed oil (SO) in randomised order for periods of 3 weeks followed by a RO test meal. In the postprandial state the concentrations of cholesterol and triacylglycerol (TAG) in TRL were higher after consumption of OO compared with RO and SO (P<0·04), possibly related to differences in the fasting state. The propagation rates for VLDL and LDL oxidation were higher in the postprandial compared with the fasting state irrespective of diet. In the fasting state, the propagation rates were highest after SO (P<0·001), and in the postprandial state, SO gave rise to a shorter VLDL lag time (P=0·03) and a higher propagation rate than OO consumption (P=0·04). Overall, the SO diet resulted in a higher postprandial propagation rate of LDL (P<0·001) compared with RO and OO, while there was no effect of diet on LDL oxidation lag time. Our results suggest that RO and SO diets lower the postprandial cholesterol and TAG concentrations compared with OO, while RO and OO diets result in similar and lowerin vitrosusceptibility to oxidation of lipoproteins than SO.
High-carbohydrate–low-glycaemic index dietary advice improves glucose disposition index in subjects with impaired glucose tolerance
Authors: Wolever Thomas M. S. , Mehling Christine
Published: January 2004

Controversy exists about the optimal amount and source of dietary carbohydrate for managing insulin resistance. Therefore, we compared the effects on insulin sensitivity (SI), pancreatic responsivity (AIRglu) and glucose disposition index (DI=SI×AIRglu) of dietary advice aimed at reducing the amount or altering the source of dietary carbohydrate in subjects with impaired glucose tolerance (IGT). Subjects were randomized to high-carbohydrate–high-glycaemic index (GI) (high-GI, n 11), high-carbohydrate–low-GI (low-GI, n 13), or low-carbohydrate–high-monounsaturated fat (MUFA, n 11) dietary advice, with SI, AIRglu and DI measured using a frequently sampled, intravenous glucose tolerance test before and after 4 months treatment. Carbohydrate and fat intakes and diet GI, respectively, were: high-GI, 53 %, 28 %, 83; low-GI, 55 %, 25 %, 76; MUFA, 47 %, 35 %, 82. Weight changes on each diet differed significantly from each other: high-GI, -0·49 (SEM 0·29) KG; LOW-GI, -0·19 (sem 0·40) kg; MUFA +0·27 (sem 0·45) kg. Blood lipids did not change, but glycated haemoglobin increased significantly on MUFA, 0·02 (sem 0·11) %, relative to low-GI, -0·19 (sem 0·08) %, and high-GI, -0·13 (sem 0·14) %. Diastolic blood pressure fell by 8 mmHg on low-GI relative to MUFA (P=0·038). Although SI and AIRglu did not change significantly, DI, a measure of the ability of β-cells to overcome insulin resistance by increasing insulin secretion, increased on low-GI by >50 % (P=0·02). After adjusting for baseline values, the increase in DI on low-GI, 0·17 (sem 0·07), was significantly greater than those on MUFA, -0·09 (sem 0·08) and high-GI, -0·03 (sem 0·02) (P=0·019). Thus, the long-term effects of altering the source of dietary carbohydrate differ from those of altering the amount. High-carbohydrate–low-GI dietary advice improved β-cell function in subjects with IGT, and may, therefore, be useful in the management of IGT.
Dietary fat source regulatesobgene expression in white adipose tissue of rats under hyperphagic feeding
Authors: Rodríguez Víctor M. , Picó Catalina , Portillo María P. , Teresa Macarulla M. , Palou Andreu
Published: January 2004

This work was designed to investigate the effect of different lipid sources onobgene expression and serum leptin levels in rats with two different feeding protocols: (1) free access to food; or (2) energy-controlled feeding. Male Wistar rats were fed diets containing 40 % energy as fat (olive oil, sunflower oil or beef tallow), for 4 weeks. In Expt 1 rats had free access to food, and in Expt 2 rats were fed a controlled amount of food (16 g/d, equivalent to 300 kJ/d). Insulin and leptin were determined by ELISA andobmRNA by Northern blot. When rats had free access to food,obmRNA levels were higher in animals fed either olive oil or sunflower oil than in those fed beef tallow. In marked contrast with feedingad libitum, no differences were found among dietary fat groups in rats fed energy-controlled diets. When both feeding protocols were compared, free access to food induced an increased expression ofobmRNA in perirenal and/or epididymal adipose tissues from rats fed either olive oil or sunflower oil, but not from rats fed beef tallow. Dietary lipid type did not induce modifications in serum leptin concentrations. A tendency to higher serum leptin levels was observed more in rats with free access to food than in rats fed energy-controlled feeding. No differences were found in insulin levels. Dietary fat type importantly affectsobmRNA expression in rat white adipose tissue under hyperphagic conditions. Further study is needed in order to elucidate the mechanism underlying this effect.
Alcohol energy intake and habitual physical activity in older adults
Authors: Westerterp Klaas R. , Meijer Erwin P. , Goris Annelies H. C. , Kester Arnold D. M.
Published: January 2004

Alcohol forms a significant component of many diets and it supplements rather than displaces daily energy intake. Surprisingly, alcohol intake does not systematically increase body weight. The present study assessed whether a higher level of habitual physical activity in the daily environment is associated with a higher alcohol intake. Alcohol intake as part of total food intake was measured with a 7 d dietary record while at the same time physical activity was monitored with a tri-axial accelerometer for movement registration. Subjects were twenty women and twenty-four men, aged 61±5 years, of BMI 27·1±4·6 kg/m2. Between subjects, there was a positive association between the level of habitual physical activity and alcohol intake (r 0·41; P<0·01). The subjects with higher alcohol intake had a higher activity level. On days with and days without alcohol consumption there was no difference in physical activity within subjects. In conclusion, it was shown that subjects with higher alcohol consumption are habitually more active. This may explain the lack of increasing body weight through additional energy intake from alcohol.
Selenium and its relationship to cancer: an update
Authors: Whanger P. D.
Published: January 2004

Selenomethionine (Semet) is the major seleno-compound in cereal grains and enriched yeast whereas Se-methylselenocysteine (SeMCYS) is the major seleno-compound in Se-accumulator plants and some plants of economic importance such as garlic and broccoli exposed to excess Se. Animals can metabolize both Semet and SeMCYS. Epidemiological studies have indicated an inverse relationship between Se intake and the incidence of certain cancers. Blood or plasma levels of Se are usually lower in patients with cancer than those without this disorder, but inconsistent results have been found with toenail-Se values and the incidence of cancer. There have been eight trials with human subjects conducted on the influence of Se on cancer incidence or biomarkers, and except for one, all have shown a positive benefit of Se on cancer reduction or biomarkers of this disorder. This is consistent with about 100 small-animal studies where Se has been shown to reduce the incidence of tumours in most of these trials. Se-enriched yeast is the major form of Se used in trials with human subjects. In the mammary-tumour model, SeMCYS has been shown to be the most effective seleno-compound identified so far in reduction of tumours. Several mechanisms have been proposed on the mechanism whereby Se reduces tumours. Even though SeMCYS was shown to be the most effective seleno-compound in the reduction of mammary tumours, it may not be the most effective seleno-compound for reduction of colon tumours.
The effect of a high-protein, high-sodium diet on calcium and bone metabolism in postmenopausal women and its interaction with vitamin D receptor genotype
Authors: Harrington Mary , Bennett Teresa , Jakobsen Jette , Ovesen Lars , Brot Christine , Flynn Albert , Cashman Kevin D.
Published: January 2004

The influence of a high-Na, high-protein (calciuric) diet on Ca and bone metabolism was investigated in postmenopausal women (aged 50–67 years) who were stratified by vitamin D receptor (VDR) genotype. In a crossover trial, twenty-four women were randomly assigned to a diet high in protein (90 g/d) and Na (180 mmol/d) or a diet adequate in protein (70 g/d) and low in Na (65 mmol/d) for 4 weeks, followed by crossover to the alternative dietary regimen for a further 4 weeks. Dietary Ca intake was maintained at usual intakes (about 20 mmol (800 mg)/d). Urinary Na, K, Ca, N and type I collagen cross-linked N-telopeptide (NTx; a marker of bone resorption), plasma parathyroid hormone (PTH), serum 25-hydroxycholecalciferol (25(OH)D3), 1,25-dihydroxycholecalciferol (1,25(OH)2D3), osteocalcin and bone-specific alkaline phosphatase (B-Alkphase) were measured in 24 h urine samples and fasting blood samples collected at the end of each dietary period. The calciuric diet significantly (P<0·05) increased mean urinary Na, N, K, Ca and NTx (by 19 %) compared with the basal diet, but had no effect on circulating 25(OH)D3, 1,25(OH)2D3, PTH, osteocalcin or B-Alkphase in the total group (n24). There were no differences in serum markers or urinary minerals between the basal and calciuric diet in either VDR genotype groups. While the calciuric diet significantly increased urinary NTx (by 25·6 %,P<0·01) in thef+ VDR group (n10; carrying one or more (f)FokI alleles), it had no effect in thef− VDR group (n14; not carrying anyFokI alleles). It is concluded that the Na- and protein-induced urinary Ca loss is compensated for by increased bone resorption and that this response may be influenced by VDR genotype.
Responses of domestic fowl to excess iodine: a review
Authors: Lewis P. D.
Published: January 2004

Typically, poultry diets contain 1–2 mg I/kg, but higher concentrations are sometimes used to enhance the I content of eggs. In addition to an increased deposition of I in the yolk, other often adverse responses occur, especially at exceptionally high concentrations. Excess I in grower diets can prevent sexual maturation in male and female fowl, and in layer diets will progressively reduce egg production until, by about 2500 mg I/kg diet, ovulation is inhibited and egg production ceases. Most I accumulates in the thyroid gland, and it is likely that the mechanism responsible for these reproductive disorders involves a modification of thyroid hormone activity. Simultaneous with the declining rate of lay, feed intake declines, egg weight and yolk-cholesterol contents decrease and body weight increases. Whereas fertility is unaffected in female breeders, hatch of fertile eggs is reduced, hatch time extended and embryonic mortality and dead-in-shell proportions increased. In contrast, male fertility is decreased because of an increased incidence of dead spermatozoa, although hatchability of eggs from normally fed hens is unaffected. All reproductive variables, together with feed intake and body weight, are normalised within about 7 d of returning to a diet with normal I levels. Excess I suppresses growth in meat-type chickens, but does not affect feed conversion efficiency. There are transient increases in plasma I and cholesterol concentration during excess I intake in all types of bird. The evidence for varying responses to different I sources is equivocal, but the consensus is that source is probably not important.
Comparison of urinary monitoring, faecal monitoring and erythrocyte analysis of stable isotope labels to determine magnesium absorption in human subjects
Authors: Bohn Torsten , Walczyk Thomas , Davidsson Lena , Pritzkow Wolfgang , Klingbeil Patrick , Vogl Jochen , Hurrell Richard F.
Published: January 2004

We have evaluated urinary monitoring and erythrocyte analysis to determine Mg absorption in human subjects as alternatives to the conventional technique of faecal monitoring by stable-isotope techniques. Ten healthy adults received 2·2 mmol 25Mg in water, together with wheat bread, followed 15 min later by intravenous injection of 0·6 mmol 26Mg (day 1). Brilliant blue and Yb (given on day 0 and day 1 respectively) served as qualitative and quantitative faecal markers. Urine was collected for 6 d after test meal intake. Complete collections of faeces were made until excretion of the second brilliant blue marker (given on day 7). Mg isotope ratios were determined by thermal ionisation-MS in urine and faeces and by inductively coupled plasma-MS in erythrocytes. Absorption was determined based on: (1) 6 d urine pools; (2) 24 h urine pools (collected 22–46 h after test meal intake); (3) erythrocytes from a blood sample drawn on day 14; (4) complete 6 d faecal pools; (5) faecal pools based on the first three consecutive stools after excretion of the first brilliant blue marker. Differences in mean Mg absorption (42 44 %) were statistically insignificant between techniques, except when based on 6 d urine pools for which the value was significantly lower (33 (sd 7) %, P=0·0003, ANOVA). The results indicate that Mg absorption can be determined from 24 h urine pools or erythrocytes obtained 14 d after test meal intake, an alternative method to the more time-consuming and labour-intense faecal monitoring. The choice of technique depends on practical and financial considerations.
Long-term vitamin C supplementation has no markedly favourable effect on serum lipids in middle-aged Japanese subjects
Authors: Kim Mi Kyung , Sasaki Satoshi , Sasazuki Shizuka , Okubo Shunji , Hayashi Masato , Tsugane Shoichiro
Published: January 2004

Antioxidant vitamins have been reported to be associated with an improvement in blood lipid profiles, but results are not consistent. The present study was designed to determine whether long-term vitamin C supplementation could alter serum lipid concentrations in subjects who completed a 5-year population-based double-blind intervention trial. A total of 439 Japanese subjects with atrophic gastritis initially participated in the trial using vitamin C and β-carotene to prevent gastric cancer. Before and upon early termination of β-carotene supplementation, 134 subjects dropped out of the trial; finally, 161 subjects assigned to the high-dose group (500 mg vitamin C/d) and 144 subjects assigned to the low-dose group (50 mg vitamin C/d) were studied. No favourable effect of vitamin C supplementation on serum concentrations of total cholesterol, HDL- and LDL-cholesterol, and triacylglycerol was observed, although high-dose vitamin C supplementation increased serum vitamin C concentrations substantially. Among women, the mean change in serum triacylglycerol decreased (−0·12 mmol/l, 95 % CI −0·32, 0·09) in the high-dose group, but increased (+0·12 mmol/l, 95 % CI 0·03, 0·22) in the low-dose group. In addition, the mean change in serum triacylglycerol among women with hypertriacylglycerolaemia was statistically significant (−1·21, 95 % CI −2·38, −0·05) after high-dose vitamin C supplementation. The 5-year vitamin C supplementation had no markedly favourable effects on the serum lipid and lipoprotein profile. However, our present results do not preclude the possibility that vitamin C supplementation may decrease triacylglycerol concentrations among women with hypertriacylglycerolaemia.
Oxyphytosterols are present in plasma of healthy human subjects
Authors: Grandgirard André , Martine Lucy , Demaison Luc , Cordelet Catherine , Joffre Corinne , Berdeaux Olivier , Semon Etienne
Published: January 2004

The oxidised derivatives of phytosterols (oxyphytosterols) were identified in plasma samples from thirteen healthy human volunteers, using MS. All the samples contained noticeable quantities of (24R)-5β,6β-epoxy-24-ethylcholestan-3β-ol (β-epoxysitostanol) and (24R)-ethylcholestan-3β,5α,6β-triol (sitostanetriol) and also trace levels of (24R)-5α,6α-epoxy-24-ethylcholestan-3β-ol (α-epoxysitostanol), (24R)-methylcholestan-3β,5α,6β-triol (campestanetriol) and (24R)-ethylch olest-5-en-3β-ol-7-one(7-ketositosterol). The amounts of these oxyphytosterols in plasma varied from 4·8 to 57·2 ng/ml. There are two possibilities concerning the origin of these compounds. First, they could come from the small amounts of oxyphytosterols in food. Second, they could originate from thein vivooxidation of phytosterols in plasma. Very few data actually exist concerning these compounds. Their identification in human samples suggests that further research is necessary in this field.
Antioxidant supplementation preserves antioxidant response in physical training and low antioxidant intake
Authors: Palazzetti Stéphane , Rousseau Anne-Sophie , Richard Marie-Jeanne , Favier Alain , Margaritis Irène
Published: January 2004

The present controlled-training double-blind study (supplemented (S) group,n7; placebo (P) group,n10) was designed to investigate whether an antioxidant mixture (Se 150 μg, retinyl acetate mg, ascorbic acid 120 mg, α-tocopheryl succinate) would allow overloaded triathletes to avoid adaptation failure in the antioxidant system. Dietary intakes were recorded. The supplement of Se, and vitamins A and E provided 100 % of the French RDA. Four weeks of overloaded training (OT) followed 4 weeks of normal training (NT). After NT and OT, biological studies were conducted at rest and after a duathlon test (run 5 km, cycle 20 km, run 5 km). During the 4-week period of NT, blood levels of GSH levels increased in response to supplementation (P<0·05) and remained elevated during OT. Plasma glutathione peroxidase activity was significantly higher in the S group in all situations after NT and OT (P<0·01). The S group had increased erythrocyte Cu,Zn-superoxide dismutase activity in response to OT (P<0·05). Supplementation significantly reduced (P<0·05) the magnitude in duathlon-induced creatine kinase isoenzyme MB mass increase, which tended to be higher with OT (P=0·09). We conclude that the antioxidant mixture helped to preserve the antioxidant system during an OT-induced stress in subjects with initially low antioxidant intakes. Effects of supplementation during NT and/or OT are shown mostly by the alleviated muscle damage. The effects of the antioxidant mixture were observed for doses that can be provided by a diversified and well-balanced diet. The maintenance of normal nutritional status with regard to the antioxidant intake (Se, vitamins C and E) plays a key role in antioxidant adaptive effects during NT and OT.
DNA damage and susceptibility to oxidative damage in lymphocytes: effects of carotenoidsin vitroandin vivo
Authors: Astley Siân B. , Hughes David A. , Wright Anthony J. A. , Elliott Ruan M. , Southon Susan
Published: January 2004

Reports on the effects of carotenoids are conflicting. The present paper examines similarities and differences from contiguous studiesin vitroandin vivo. Single-cell gel electrophoresis was used to measure the frequency of single-strand breaks (SSB) in the cell line MOLT-17 (as a model system) and human peripheral blood lymphocytes (PBL). MOLT-17 cells were supplemented with β-carotene, lutein or lycopene at a range of concentrations (0·00–8·00 μmol/l) using a liposome delivery method. Uptake was dose-dependent. β-Carotene concentration in the media had no effect on SSB in control cells, but incubation with lycopene or lutein (>2·00 μmol/l) increased the numbers of SSB in control cells. MOLT-17 DNA was less susceptible to oxidative damage (100 μmol H2O2/l, 5 min, 4 °C) following incubation with carotenoids between 0·50 and 1·00 μmol/l; at >1·00 μmol/l the effects were ambiguous. Apparently healthy male volunteers supplemented their habitual diets with lutein, β-carotene or lycopene (natural isolate capsules, 15 mg/d, 4 weeks) in three independent studies, raising plasma concentrations to different extents. Lycopene and lutein had no effect on SSB in control PBL or following oxidative challenge. However, increased plasma β-carotene was associated with more SSB in control cells whilst PBL DNA resistance to oxidative damageex vivowas unaffected. These results suggest that the carotenoids are capable of exerting two overlapping but distinct effects: antioxidant protection by scavenging DNA-damaging free radicals and modulation of DNA repair mechanisms.
Prenatal programming of angiotensin II type 2 receptor expression in the rat
Authors: McMullen Sarah , Gardner David S. , Langley-Evans Simon C.
Published: January 2004

Exposure to undernutrition during fetal life has been proposed as an underlying cause of adult hypertension. Epidemiological studies demonstrating relationships between low birth weight and later CVD are supported by animal experiments indicating that manipulations of the maternal diet in pregnancy exert programming effects upon blood pressure control. Pregnant female Wistar rats were fed a control diet (n 13) or a low-protein diet (n 12) throughout pregnancy. At delivery all animals were fed the same standard laboratory chow diet. Analysis of nephron number in kidneys obtained from 4-week-old offspring showed that this was significantly (P<0·05) reduced in animals exposed to maternal protein restriction. At this age rats exposed to low-protein diets in utero had systolic blood pressures that were significantly greater than those of control animals (+23 mmHg, P<0·05). Administration of ascending doses of angiotensin II (1–40 ng/kg body weight intravenously) to 10-week-old anaesthetised female rats showed that the pressor response to the peptide was greater and more prolonged in animals exposed to low-protein diets in utero. Renal expression of mRNA for the angiotensin II type 1A receptor was similar in the two groups of rats, but low-protein-exposed animals had significantly lower renal expression of the type 2 receptor (P=0·023). These results suggest that maternal nutritional status programmes expression of the renal angiotensin II type 2 receptor. This may play a key role in the impairment of renal development and the elevation of blood pressure noted in rats exposed to intra-uterine protein restriction.
β-Carotene–vitamin A equivalence in Chinese adults assessed by an isotope dilution technique
Authors: Wang Zhixu , Yin Shian , Zhao Xianfeng , Russell Robert M. , Tang Guangwen
Published: January 2004

The present study was carried out to determine the conversion factor of synthetic2H-labelled β-carotene to vitamin A in Chinese adults by using a stable-isotope dilution technique. Fifteen healthy volunteers aged 50–60 years were recruited for a 55 d experiment. The volunteers (nine males and six females) were each given a physiological dose of [2H8]β-carotene (6 mg) in oil on the first day of the experiment, and a reference dose of [2H8]retinyl acetate (3 mg) in oil was given on the fourth day. Serum samples were collected at 0, 3, 5, 7, 9, 11, and 13 h on the first and the fourth days of the study, daily for 10 d, and then weekly from days 14 to 56. β-Carotene and retinol were extracted from serum and isolated by HPLC, and their enrichments were respectively determined by using GC–electron capture negative chemical ionisation-MS and LC–atmospheric pressure chemical ionisation interface-MS. Four of the subjects exhibited β-carotene to vitamin A conversion factors of >29·0:1 on a molar basis and were termed ‘poor converters’. In the eleven normal converters (seven males and four females), the calculated conversion factors of β-carotene to retinol ranged from 2·0:1 to 12·2:1 with an average of 4·8 (sd 2·8):1 on a molar basis, and from 3·8:1 to 22·8:1 with an average of 9·1 (sd 5·3):1 on a weight basis. The 52 d post-intestinal absorption conversion was estimated to be about 30 % of the total converted retinol.
Effect of equilibrated hydration changes on total body water estimates by bioelectrical impedance analysis
Authors: Pialoux Vincent , Mischler Isabelle , Mounier Remi , Gachon Pierre , Ritz Patrick , Coudert Jean , Fellmann Nicole
Published: January 2004

The present study was performed to determine how equilibrated fluctuations in hydration affected the validity of bioelectrical impedance analysis (BIA) for body composition assessment. Total body water (TBW) expansion was induced by a 4 d endurance trial and the subsequent water loss was obtained over the recovery period. Twelve healthy men exercised on a cycle and treadmill alternately for 5 h/d over 4 d at moderate intensity. TBW, fat mass (FM) and fat-free mass (FFM) were assessed 3 d before the trial (control), and on the first and eighth day of recovery (R1 and R8 respectively). TBW was evaluated by 2H dilution (TBW2H) as a reference method and by BIA (TBWBIA) at 100 kHz at the same time. TBW2H increased significantly between the control day and R1 by 1·87 (sd 1·11) litres (P=0·005) and TBWBIA by 1·38 (sd 1·56) litres (P=0·009). Both values returned to the control level on R8. For each period, TBW2H and TBWBIA did not differ significantly and were correlated (r2 0·85, P=0·0004 for the control day; r2 0·63, P=0·03 for R1; r2 0·75, P=0·02 for R8). Plasma Na concentration and osmolality did not differ between the control day, R1 and R8. FFM gain (1208 (sd 1983) g) and FM loss (−1168 (sd 906) g) between the control day and R1 were followed by a FFM decrease (−624 (sd 1281) g) and a FM increase (860 (sd 1212) g) between R1 and R8. As expected, these FFM and FM changes were significantly correlated with TBW variations. The present results provide evidence that BIA may be a useful method for estimating TBW when fluid shifts are equilibrated and electrolyte concentrations are unchanged. However, it is not a valid technique for assessing FM and FFM under these conditions.
A micronised, dispersible ferric pyrophosphate with high relative bioavailability in man
Authors: Fidler Meredith C. , Walczyk Thomas , Davidsson Lena , Zeder Christophe , Sakaguchi Noboru , Juneja Lekh R. , Hurrell Richard F.
Published: January 2004

Ferric pyrophosphate is a water-insoluble Fe compound used to fortify infant cereals and chocolate-drink powders as it causes no organoleptic changes to the food vehicle. However, it is only of low absorption in man. Recently, an innovative ferric pyrophosphate has been developed (Sunactive Fe™) based on small-particle-size ferric pyrophosphate (average size 0·3 μm) mixed with emulsifiers, so that it remains in suspension in liquid products. The aim of the present studies was to compare Fe absorption of micronised, dispersible ferric pyrophosphate (Sunactive Fe™) with that of ferrous sulfate in an infant cereal and a yoghurt drink. Two separate Fe absorption studies were made in adult women (ten women/study). Fe absorption was based on the erythrocyte incorporation of stable isotopes (57Fe and58Fe) 14 d after the intake of labelled test meals of infant cereal (study 1) or yoghurt drink (study 2). Each test meal was fortified with 5 mg Fe as ferrous sulfate or micronised, dispersible ferric pyrophosphate. Results are presented as geometric means. There was no statistically significant difference between Fe absorption from micronised, dispersible ferric pyrophosphate- and ferrous sulfate-fortified infant cereal (3·4 and 4·1 % respectively;P=0·24) and yoghurt drink (3·9 and 4·2 % respectively;P=0·72). The results of the present studies show that micronised, dispersible ferric pyrophosphate is as well absorbed as ferrous sulfate in adults. The high relative Fe bioavailability of micronised, dispersible ferric pyrophosphate indicates the potential usefulness of this compound for food fortification.