Comparison of fat oxidation during exercise in lean and obese pubertal boys: clinical implications.

OBJECTIVE: To examine fat oxidation rates during exercise in lean and obese pubescent children. DESIGN: A graded leg cycle ergometry test was performed by two groups of pubescent boys (13 lean: mean (SD) age 12.0 (0.5) years, body mass index (BMI) 18.56 (1.12) kg/m(2); 17 obese: mean (SD) age 12.1 (0.1) years, BMI 26.68 (3.37) kg/m(2); p<0.001). The first step of the test was fixed at 30 W and power was gradually increased by 20 W every 3.5 min. The mean ventilatory gas measurement was obtained during the last 30 s of each step for calculation of fat oxidation rate vs exercise intensity. RESULTS: At low intensity (0-30% of peak oxygen consumption) when fat-free mass is considered, the fat oxidation rate was identical for the two groups. At higher intensities (40%, 50% and 60% of peak oxygen consumption) the fat oxidation rate was significantly higher in lean boys than in obese boys. CONCLUSION: These results confirm that obese pubertal boys have fat-free mass decreased capacities to use fat during moderate exercise. The findings suggest that obese boys need to practise physical activity at a lower intensity than healthy boys to enhance lipolysis and diminish adipose tissue and the consequences of obesity.

Interactions between ethylenediaminetetraacetic acid (EDTA) and iron absorption pathways, in the Caco-2 model.

UNLABELLED: EDTA is a well known enhancer of iron absorption; however, the precise way of absorption of iron ingested in presence of EDTA is not known; some data suggest it could use a passive, non regulated paracellular way. Iron (sulphate or gluconate) absorption by Caco-2 cells was assessed in presence of EDTA. EDTA did not change the apical uptake of iron; transport in the basal chamber increased by 98% for FeSO4 and 95% for Fe gluconate. By contrast, intracellular storage decreased by 31% for FeSO4 and 64% for Fe gluconate. In addition EDTA induced a significant increase of permeability of the cell monolayer assessed by a decrease of transepithelial electrical resistance: 314+/-34 Omegacm(-2) to 235+/-57 Omegacm(-2) for sulphate, 414+/-33 Omegacm(-2) to 223+/-36 Omegacm(-2) for gluconate; iron free control: 410+/-10 Omegacm(-2). CONCLUSIONS: These results suggest that in presence of EDTA iron absorption occurs mainly by the paracellular instead of the regulated cellular way, that could potentially enhance its toxicity.

Different segmental transit times in patients with irritable bowel syndrome and "normal" colonic transit time: is there a correlation with symptoms?

BACKGROUND: The Rome criteria serve as gold standard for establishing a diagnosis of irritable bowel syndrome (IBS), but only represent a cluster of symptoms. On the other hand, measurement of colonic transit time (CTT) with radiopaque markers is a solid and more objective method to quantify functional abnormalities. The goal of this study was to investigate whether the IBS symptoms, as defined in the Rome II criteria, correspond to objective physiological parameters, i.e. CCTs. METHODS: The study enrolled 148 healthy control subjects and 1385 consecutive IBS patients. Transit times were measured for the whole rectocolon (overall CTT) and for 3 segments (right colon, left colon, rectosigmoid area); segmental distribution of markers and diffusion coefficients were also assessed. In order to analyze homogeneous groups, we restricted analysis to subjects with "normal" CTT (< or =70 hours). RESULTS: Six hundred forty four IBS patients (46%) and 14 control subjects (9%) had CTT >70 h and were eliminated. In subjects with CTT < or =70 h, CTT did not follow a normal (Gaussian) distribution. We identified 3 different CTT clusters in healthy controls and 4 clusters in IBS patients. Even if CTT was not significantly different between clusters, each cluster was characterized by a specific pattern of segmental colonic transit. There was a marked gender difference: women had longer overall CTT values than men, both in control and IBS patient groups (p<0.001). However, female IBS patients had significantly shorter colorectal transit times than female controls (p<0.001), as well as faster transit than in men through the left colon and rectosigmoid area. There were no significant differences in transit time between male IBS patients and male controls with the exception of a faster rectal transit in IBS patients (p<0.01). There was no association between segmental colonic transit values and sign or symptoms comprising the Rome II criteria. CONCLUSIONS: In subjects with CTT < or =70 h, CTT does not follow a normal distribution but is clustered in subgroups that can be distinguished only by measuring segmental colonic transit. Within these subgroups, there is a marked difference in transit times between IBS patients and normal subjects, suggesting that IBS patients with "normal" CTT are not "normal". The Rome II criteria do not reflect differences in segmental transit times in IBS patients with "normal" CTT. We therefore propose to evaluate segmental transit times in IBS patients with "normal" CTT, before and after treatment, in order to correctly interpretate variations in signs and symptoms. These findings have important implications in evaluating the effect of drugs on bowel function and should help define better inclusion criteria for studies evaluating new drugs for the treatment of IBS.

Iron availability and consumption of tea, vervain and mint during weaning in Morocco.

BACKGROUND/AIMS: Iron deficiency impairs growth and psychomotor development of infants. In Morocco, infusions are introduced very early in infant diet, and could contribute to iron deficiency, due to their high polyphenol content. METHODS: The availability of tea, mint and vervain infusions was assessed using an in vitro model of digestion and dialysis. Two gastric pHs were used: pH 4 as in the first week life, and pH 2.5 as in older infants. Six repetitions of each experiment were made. The total polyphenol content of infusions was measured. RESULTS: At pH 4 and at pH 2.5, iron availability was decreased by tea and vervain, and increased by mint and ascorbic acid. At both pHs it was increased by addition of ascorbic acid to tea and vervain. In addition, at pH 2.5 it was increased by addition of ascorbic acid to mint. The highest value was observed in the presence of both ascorbic acid and mint (33.1 +/- 4.1%). In any case, iron availability was higher at pH 2.5 than at pH 4 (with single compounds or combinations with ascorbic acid). The polyphenol contents (mg/l) of tea, vervain and mint infusions were 2,236.1, 771.1, and 16.5. CONCLUSIONS: Tea and vervain infusions inhibited iron availability. In contrast, mint improved it; vitamin C helped in preventing these inhibiting properties. It could be proposed to discourage tea and vervain drinking at early weaning and to replace them by mint infusion, or at least to promote the consumption of vitamin C-rich fruit juice to counteract these inhibiting effects.

Influence of short-chain fatty acids on iron absorption by proximal colon.

BACKGROUND: Short-chain fatty acids produced by bacterial fermentation in the colon enhance the local absorption of cations, such as calcium, that could be used to improve the bioavailability of iron if a significant colonic absorption of iron were to occur. METHODS: Iron (iron gluconate, 100 microM) absorption by the caecum of the rat was compared with that in proximal sites of the small bowel using the Ussing chamber model; the influence of probiotic bacteria (Propionibacterium freudenreichii) on iron absorption was assessed and compared with that of two of their fermentation products (acetic and propionic acids) using the Ussing chamber and the ligated colon with gamma emitting iron as experimental models. RESULTS: The caecum absorbed less iron than the duodenum, but significantly more than the jejunum and ileum. This occurred mainly through an enhanced mucosal transfer of iron uptake. Propionibacteria enhanced iron absorption from the proximal colon; the same effect was observed in the presence of viable bacteria, or the culture medium free of viable bacteria, or acetate and propionate or propionate alone. CONCLUSIONS: The proximal colon could be a significant site available for iron absorption; this absorption can be enhanced by local production of short-chain fatty acids such as propionate.

Aluminium increases xanthine oxidase activity and disturbs antioxidant status in the rat.

The mechanisms responsible for the neurotoxic effects of Al remain poorly understood. In order to determine whether Al promotes oxidative stress in vivo, we measured the enzymatic activity of xanthine oxidase (XO), superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione-S-transferase (GST) and glutathione reductase (GR) in four groups of rats after eight days of intraperitoneal administration of variable concentrations of Al (0, 5, 10, and 15 mg/kg body weight, respectively). XO activity was measured in both plasma and liver samples, and the activities of the remaining enzymes were further determined in the brain and red blood cells (RBC). The most significant changes were observed in XO and GPX activities, that were enhanced and depressed, respectively. In both instances, the enzyme activities were correlated with Al concentrations, either positively (XO) or negatively (GPX). Enhancement of XO and inhibition of GPX activity may lead to the accumulation of intermediate toxic compounds such as hydrogen peroxide and hydroxyl radicals, since SOD activity is increased as well. The latter finding must be taken with some caution because previous studies have shown contradictory results in this field. Our data suggest that Al toxicity could be mediated by its action on both pro- and anti-oxidant enzymes. The biological significance of these findings remains to be established.

Inhibition of zinc absorption by iron depends on their ratio.

Previous studies upon zinc-iron interactions gave conflicting results that could come from differences in protocol design or in trace element status of subjects. The present work assessed the influence of zinc : iron ratio and iron deficiency upon zinc absorption. The digestive absorption of zinc sulphate (100 micromol Zn/l) in presence of iron gluconate was studied in perfused jejunal loops (n = 6/group) of normal rats (range 0-1000 micromol Fe/l) and iron deficient rats (200-750 micromol Fe/l). In normal rats no significant iron inhibition on zinc absorption occurred at Fe:Zn ratio below 2:1. At higher ratios zinc uptake and net absorption decreased significantly (p<0.05). Between 2:1 and 5:1 a dose dependent inhibition of zinc absorption occurred and reached a plateau beyond this ratio. In iron deficient animals no changes in zinc uptake, mucosal retention and absorption compared to normal animals occurred at ratio 2:1. At higher ratios differences were observed at every zinc absorption step except for mucosal retention at 7.5:1 ratio. Iron-zinc interactions depend on their ratio and on previous trace elements status of subjects. Due to the wide and unknown variations that were likely to occur between the subjects of previous human and experimental studies, these results could explain some of the discrepancies between their results.

Influence of the extent of haemoglobin hydrolysis on the digestive absorption of haem iron in the rat. An in vitro study.

This study was designed to assess the haem-peptide interactions which occur during progressive haemoglobin hydrolysis by digestive enzymes and their relationship with haem iron digestive absorption. The behaviour of different haemoglobin hydrolysates was studied using the Ussing chamber model. Hydrolysates were produced from enzyme digestion of bovine haemoglobin at pH 3 by pepsin and at pH 10 by subtilisin. Samples with increasing degrees of hydrolysis (0-15 %) were studied. Biochemical assays (pyridine haemochromogen method and UV absorption spectra) were used to follow haem solubility and haem-peptide interactions in samples. Increasing the hydrolysis level of haemoglobin was associated with an enhanced iron uptake; the highest uptake rate was reached between 8 and 11 % of globin hydrolysis, whichever enzyme was used. The mechanisms rendering iron soluble and available differ between the two enzymes. The comparison between biochemical and absorption data suggests that the formation of soluble peptide-haem complexes was not sufficient to enhance haem iron absorption, since globin-bound iron is poorly absorbed; an efficient absorption occurred only when haem was loosely bound to low molecular weight peptides.

The effect of cysteine and 2,4-dinitrophenol on heme and nonheme absorption in a rat intestinal model.

Previous studies have showed that purified heme iron forms insoluble polymers that are poorly absorbed. The presence of peptides and of amino acids maintaining heme iron in a soluble form could improve its bioavailability. The digestive uptake and transfer of a concentrated hydrolysate of heme peptides (HPH) and of iron gluconate (Gluc) at 100 µM were compared in vitro in a Ussing chamber. The effects of an enhancing amino acid (L-cysteine) on the uptake and transfer of both forms were assessed. An inhibitor of the oxidative phosphorylation (2,4-dinitrophenol; DNP) was used to differentiate the active and passive mechanisms of the absorption. The mucosal uptake (%Tot) and enterocyte transfer (%S) of the two sources of iron did not differ. DNP significantly reduced %Tot and %S of both forms. Cysteine significantly enhanced %Tot and %S of HPH and Gluc, partly corrected the inhibition exerted by DNP on %Tot of HPH and %S of both forms, and fully restored %Tot of Gluc. In presence of peptides produced by globin hydrolysis, the absorption of hemoglobin iron was efficient; it was mostly energy dependent and, therefore, should have occurred by a regulated transcellular pathway. Cysteine enhanced the passive uptake of iron and the passive processes involved in the enterocyte transfer of the common pool made of both sources (heme and nonheme) of iron. These results showed that heme iron can be purified and concentrated without impairing its digestive absorption, provided it remains in presence of peptides or amino acids.

Iron tissue storage and hemoglobin levels of deficient rats repleted with iron bound to the caseinophosphopeptide 1-25 of beta-casein.

Caseinophosphopeptides (CPP) issued from enzyme digestion of caseins bind cations and keep them soluble in the digestive tract. They could be used as ligands to improve iron (Fe) bioavailability. Fe-deficient young rats were repleted with Fe (40 or 200 mg/kg of diet) bound either to the beta-CN (1-25) of beta-casein or to whole beta-casein or as FeSO(4). A control pair-fed group was given 200 mg of Fe (FeSO(4))/kg of diet for 6 weeks. After repletion, hemoglobin concentration of the control group was reached only by the ) animals fed 200 mg of Fe/kg; beta-CN (1-25) bound Fe (40 and 200 mg) produced higher Fe liver and spleen stores than FeSO(4). Binding Fe to the whole, nonhydrolyzed beta-casein gave results intermediate between the other experimental groups. Binding Fe to phosphoserine residues of low molecular weight CPP improved its ability to cure anemia and to restore iron tissue stores, as compared to Fe bound to the whole casein and to inorganic salts.

A comparative study of esophageal and anorectal motility in myotonic dystrophy.

Myotonic dystrophy may be associated with visceral abnormalities involving smooth muscle, the pathogenesis of which is not clear. Our aim was to evaluate the involvement of smooth and striated muscles at both ends of the gastrointestinal tract. Esophageal and anorectal manometric studies were performed in 13 patients and healthy controls. There was a correlation between: (1) the resting pressure in the upper esophageal sphincter and in the lower anal canal, (2) the amplitude and the coordination of contraction primary waves in the proximal and in the distal esophagus, and (3) the resting pressure in the higher anal canal and in the lower one. These results suggest that both ends of the gastrointestinal tract are disturbed in a similar fashion, both quantitatively and qualitatively and that there is a relationship between smooth and striated visceral muscle involvement in myotonic dystrophy.

Effect of propionibacteria supplementation on fecal bifidobacteria and segmental colonic transit time in healthy human subjects.

BACKGROUND: Some strains of Propionibacterium have bifidogenic properties and enhance gut motility in the animal. However, they are not part of the indigenous fecal flora. This study was designed to assess the digestive survival of ingested propionibacteria, their bifidogenic properties, and the resulting changes in colonic transit time in healthy humans. METHODS: Eighteen subjects were given 5 . 10(10) CFU propionibacteria/day during 2 weeks. Fecal concentrations of propionibacteria and bifidobacteria were counted before (day -8, day -1), during (day 7, day 14), and after (day 21, day 28) the supplementation. Colonic transit time was measured before and at the end of the 1st week of supplementation. RESULTS: Basal counts of propionibacteria were less than 5 log CFU/ml stools. They increased in 15 subjects to (mean+/-1 standard deviation) 5.63+/-0.71 and 6.37+/-0.89 on day 7 (P < 0.01) and day 14 (P < 0.01) and returned to basal levels on day 21. Basal counts of bifidobacteria (mean, 7.94+/-0.71) increased to 8.39+/-0.97 on day 7, 8.36+/-0.86 on day 14, and 8.70+/-0.95 on day 21 (P < 0.05 from mean basal count) and returned to pretreatment levels on day 28 (7.88+/-1.38). Mean counts of propionibacteria during supplementation and bifidobacteria levels on day 14 were significantly correlated (P = 0.01). Transit time did not change in the right colon (17.4+/-8.1 h versus 17.3+/-8.3 h) or in the rectosigmoid area(12.8+/-8.5 versus 13.3+/-0.2 h); left colon transit was significantly slowed (7.0+/-5.0 h versus 11.9+/-9.4 h; P < 0.05). CONCLUSIONS: Part of the ingested propionibacteria were able to survive the digestive transit. This supplementation was associated with changes in segmental colonic motility, yet the mechanisms involved in these changes remain unknown.

Long-term effects of iron:zinc interactions on growth in rats.

The influence of iron (Fe) on the bioavailability and functional status of zinc (Zn) was studied in young rats using metabolic balances and tissue dosages, which were compared to growth. Diets supplied adequate intakes of Fe (45 and 300 mg/kg diet) and Zn (14 and 45 mg/kg) for 2 mo. Two metabolic balance determinations were performed that were correlated for Zn and Fe during the first and the last weeks of the study. A significant effect of Fe supply, but not of Zn was displayed on Fe absorption; both Fe and Zn diet concentrations had a significant influence on Zn absorption. Fe and Zn organ contents were significantly correlated with the amount absorbed during the two metabolic balances. There was a positive correlation between liver and muscle Fe and Fe absorption, and Fe absorption and muscle Zn, as well as a negative one with liver Zn; a positive correlation was displayed between Zn absorption and Zn organ content. No correlation was found between Zn absorption and Fe tissue content. Growth was correlated with Zn, but not with Fe absorption during both balances. A positive correlation was displayed between growth and Zn liver content, and a negative one with Fe liver content. Care must be taken to give growing subjects balanced diets or supplementation, since the negative interactions between these trace elements are likely to persist as long as the diet is given.

Sensitivity of beta-casein phosphopeptide-iron complex to digestive enzymes in ligated segment of rat duodenum.

Binding iron to the phosphorylated beta(1-25) peptide derived from beta-casein improves iron bioavailability in the rat. The aim of the present work was to learn how injected beta(1-25) and iron-beta(1-25) complex behave in the duodenum of rats using the technique of intestinal ligation in situ and reversed-phase (RP)-high performance liquid chromatography-electrospray mass spectrometry analysis of the lumen contents. The results demonstrate that beta(1-25) is sensitive to digestive enzymes including proteases/peptidases and phosphatases during duodenal transit. The lumen contents of rats perfused with iron free beta(1-25) contained all peptidic sequences derived from beta(1-25). In contrast, the phosphorylated part of beta(1-25) [i.e., beta(15-24)] was not detected in lumen of rats perfused with iron-beta(1-25) complex.

Mechanisms of absorption of caseinophosphopeptide bound iron.

Binding iron (Fe) to the 1-25 caseinophosphopeptide obtained from enzyme hydrolysis of beta casein (beta CPP) improves Fe bioavailability in the rat. To assess the mechanisms involved in its absorption, a perfused, vascularized duodenal rat loop model was used in controls and in Fe-deficient (bleeding of 25% blood volume) rats. Inhibitors of oxidative phosphorylation [2-4 dinitrophenol (DNP)] and/or of endocytosis [phenylarsine oxide (PAO)] were added to the perfusion solution containing 50 microM Fe as beta CPP bound Fe (Fe-beta CPP) or gluconate (Fe Gluc). Fe-beta CPP enhanced Fe uptake, reduced mucosal storage, and improved net absorption both in controls and in deficient animals. DNP reduced uptake, mucosal storage, and net absorption by the same percentage in Fe-beta CPP and Fe Gluc perfused rats in both control and Fe-deficient animals. PAO decreased uptake, mucosal storage, and net absorption of Fe-beta CPP but not of Fe Gluc. At the end of the experiment Fe serum levels were increased only in Fe Gluc animals. These results confirm the improved bioavailability of beta CPP bound Fe. They suggest that at least part of its absorption can occur by a different pathway than usual Fe salts. Fe-beta CPP can be taken up by endocytosis and absorbed bound to amino acids or peptides.

Improvement of zinc intestinal absorption and reduction of zinc/iron interaction using metal bound to the caseinophosphopeptide 1-25 of beta-casein.

Binding zinc (Zn) to soluble caseinophosphopeptides (CN), produced by the hydrolysis of caseins, improves its absorption and could prevent inhibition by other nutrients such as iron (Fe). The absorption of Zn (100 mumol/L) bound to the 1-25 CN (beta-CN(1-25)) of beta-casein, or as ZnSO4 was studied using the isolated, perfused rat intestinal loop system. Fe (Fe-CN or Fe gluconate (Fe Gluc)) was added at Zn/Fe ratios of 2:1, 1:5 and 1:10. Disappearance from the lumen (Q1) and net absorption (ZnAbs) of Zn-CN were statistically greater than for ZnSO4; Zn retention by the mucosa (Q2) did not significantly differ. Fe Gluc reduced Q1, Q2 and ZnAbs for ZnSO4 at ratios of 1:5 and 1:10 and for Zn-CN at a ratio of 1:10. Fe-CN reduced Q1 and ZnAbs of both forms of Zn at a ratio of 1:10; Q2 remained unchanged. Binding Zn to beta-CN(1-25) improved Zn absorption and prevented Fe from inhibiting its absorption.

Effect of stabilising amino acids on the digestive absorption of heme and non-heme iron.

We used the Ussing chamber model to study heme iron absorption by rat duodenal mucosa. Heme iron was obtained by enzymic digestion of bovine haemoglobin and concentration of heme (HPH). Its uptake and mucosal transfer was compared to iron gluconate (Gluc), at 100 microM and 1 mM. At 100 microM iron uptake (Qtot), mucosal retention (Qm) and transfer across the mucosa (Qs) was similar for the two sources of iron. Qs was significantly higher at 1 mM for Gluc but not for HPH, and was associated with higher levels of Qm. Addition of L-histidine did not improve iron absorption and indeed it decreased it if iron was provided as Gluc. L-cysteine increased the transfer of iron of both sources. In the in vitro model using rat digestive mucosa, heme iron appeared to be an efficiently used source of iron, which might prevent its accumulation by gut when supplied in excess.

Colonic transit time in patients with myelomeningocele.

To evaluate colonic motility in patients with myelomeningocele, the transit time of radiopaque markers was studied in 22 patients with myelomeningocele and 22 age and sex matched controls. Mean colonic transit time was significantly longer in patients than in controls (103.2 +/- 49 h versus 23.3 +/- 13 h; P < 10(-7). Thirteen of 22 patients with myelomeningocele were severely constipated. Six patients had constipation secondary to delayed colonic transit, particularly in the left colon, and seven had increased rectosigmoid transit. The clinical questionnaire and particularly the frequency of bowel movements did not predict colonic transit. Among 13 patients with increased colonic transit, eight had more than five bowel movements per week and, thus, six of them did not use laxatives or enemas, despite the presence of faecal incontinence. There was no relationship between colonic transit time and the level of the spinal lesion or patient mobility in patients with myelomeningocele. Rectoanal dyssynergia was found in 14 of the 22 patients, but equally often in patients with delayed rectosigmoid transit (4/7) as in the other patients (10/15) (P = ns). Uninhibited detrusor contractions were observed more often in patients with increased colonic transit time than in others (8/12 versus 1/8, P = 0.05). In the absence of a correlation between colonic transit time, clinical symptoms, anorectal motility, level of spinal lesion, patient mobility, evaluation of colonic transit of radiopaque markers should be assessed routinely in all patients with myelomeningocele to plan the most appropriate treatment, mainly in case of unhibited detrusor contractions.

Relationships between iron and zinc metabolism: predictive value of digestive absorption on tissue storage.

The responses of animals to intake of a trace element could vary if it is ingested with a single test meal or due to chronic intake. The metabolic relationships between zinc (Zn) and iron (Fe) were assessed in the young animal by comparing their digestive absorption studied at the beginning of the study with their tissue storage after two months of being fed on experimental diet. Diets supplied adequate intakes of Fe (45 and 300mg/kg diet) and Zn (14 and 45 mg/kg). A significant effect of Fe supply (p < 0.0001) but not of Zn was displayed on Fe absorption; both Fe and Zn diet concentrations influenced Zn absorption (p < 0.01, p < 0.0001). Fe and Zn organ contents significantly correlated with the amount absorbed during the metabolic balance (p < 0.0001). There was a positive correlation between liver, bone, and muscle Fe and Fe absorption (mg/d)(p < 0.0001), and Fe absorption and bone and muscle Zn (p < 0.04) and a negative one with liver Zn (p < 0.0001); a positive correlation was displayed between Zn absorption (mg/d) and Zn organ content (p < 0.0001). There was no correlation between Zn absorption and Fe tissue content (p > 0.05). This study suggests that interactions occur at every step of Fe and Zn metabolism; Fe is more efficient in altering Zn storage than the reverse. The organism seems to be unable to diminish the consequences of an unbalanced diet and digestive absorption. Care must be taken to give the young growing balanced diets.