Mineral absorption of diets containing natural carob fiber compared to cellulose, pectin and various combinations of these fibers Absorción de minerales de dietas que contienen fibra natural de algarrobas comparada con celulosa, pectina y varias combinaciones de estas fibras

The influence of the consumption of natural carob fiber (NCF), an insoluble hypocholesterolemic fiber, as the unique dietary fiber or combined with cellulose (CEL) or pectin (PEC), on mineral bioavailability was studied. Six groups of rats were fed for 10 days diets containing 10% CEL, NCF, PEC or CEL+NCF, CEL+PEC and NCF+PEC mixtures at 50%. Food intake was lower with PEC than NCF and CEL+NCF, but final body weight was unaffected. Fecal weight showed significant differ ences in the following order: CEL, NCF, CEL+NCF > CEL+PEC, NCF+PEC > PEC. Percentage of calcium absorption was higher with CEL+PEC and NCF+PEC compared with the rest of fibers. Mag nesium absorption was also significantly enhanced in these two groups compared to NCF (p < 0.0004). Iron absorption did not show variations. Zinc apparent absorption was reduced by PEC, but the NCF+PEC mixture counterbalanced this effect. Liver iron was significantly lower with NCF+PEC than CEL, and liver iron concentration was significantly lower with NCF+PEC compared to CEL+PEC. Liver zinc was significantly higher with CEL+NCF than PEC while liver zinc concentrations were slightly higher with the former (p = 0.05 compared to NCF). The results indicate that NCF, compared to CEL and PEC, did not decrease the efficiency of calcium, magnesium and iron absorption in rats, while compared to PEC it increased zinc apparent absorption. Moreover, by combining NCF with PEC calcium and magnesium, absorptions enhanced in comparison with NCF alone, which was prob ably a result of the combination of soluble and insoluble fibers.

Selected trace elements and minerals in cord blood: association with lipids and lipoproteins at birth

Recent studies have found that some minerals are associated with lipoprotein metabolism, peroxidation and coronary heart disease. The present study was designed to obtain information on the relationship between the concentrations of minerals and trace elements and those of lipids, lipoproteins and apolipoproteins (Apo) in cord blood. Seventy-nine healthy singleton normoweight full-term newborns without foetal distress according to Apgar scores were studied. The quartile distribution of neonates, according to serum concentrations of the different minerals studied, displayed significant differences in lipid values between infants in the lowest and highest quartiles of: magnesium, for HDL-cholesterol, Apo A-I, Apo B and the HDL-cholesterol/Apo A-I ratio; iron, for HDL-cholesterol and the HDL-cholesterol/Apo A-I ratio; copper, for triglycerides and the LDL-cholesterol/Apo B ratio. With the exception of calcium, several significant correlations were found between the minerals and trace elements and the lipids, Apo and lipoproteins tested.

Growth characteristics in laboratory animals fed zinc-deficient, copper-deficient, of histidine-supplemented diets

The effects of growth in male Wistar rats and female Swiss Random mice were studied during dietary zinc (Zn) deficiency, copper (Cu) deficiency, and during the feeding of a histidine (His) supplement Growth was analyzed by comparing the characteristics of the decreasing exponential growth curve plotted for the experimental period. When the animals were pair-fed the experimental diets, the growth pattern in the animals remained unaltered. The growth rate decreased during Zn deficiency by a factor of 0.64 over a period of 10 d (male young adult rats) and by a factor of 0.76 over a period of 28 d (female weaning mice). On the other hand, a supplement of His increased the growth rate by a factor of 1.11 (in the mice). The effect of Cu deficiency on the growth rate was not statistically significant (in the rats). However, Cu deficiency causes effects in the Zn status that may over-compensate minor growth retardation during Cu deficiency. The effect of the His supplement is explained by its having an effect on the Zn-absorption (His enhancing Zn transport over the gut) and by a stimulating effect of this amino acid on the thickness of the growth plate in bone.

Dietary subacute zinc deficiency and potassium metabolism

In a controlled animal experiment the effects of dietary subacute Zn deficiency on growth, Zn concentration, and tissue 42-K distribution were studied. Growth retardation caused lower body weight because both skeletal and heart muscle showed a reduction in cell mass. Zn concentrations were reduced in most tissues, however, they remained unaltered in heart muscle. 42-K activity increased in skeletal muscle and pancreas. We hypothesize the latter reflects the organs rate of metabolism, inducing the exocrine pancreas to increase Zn absorption; in skeletal muscle it may induce also alterations in cell potentiation, causing restless behavior. As suggested by the calculated specific K activity (Bq/mol), the K uptake was highest in liver and bone, high in pancreas and skeletal muscle and low in heart muscle. The latter suggests K retention in heart muscle. Specific activity in plasma and jejunum remained unaltered: K status and absorption seem unaffected. Zn deficiency causes different 42-K activities in the various tissues, that respond by alterations in K metabolism without the induction of K deficiency.

The uptake of zinc by erythrocytes under near-physiological conditions

The in vitro uptake of zinc by erythrocytes was measured under near-physiological conditions, using 65Zn as a radioactive tracer. Because of the presence of serum albumin--a strong zinc ligand--a low concentration of medium free zinc was maintained. Under these conditions a high-affinity carrier for zinc transport over the cell membrane was identified. With human erythrocytes, a Michaelis constant (Km) of 0.2 nM with respect to free medium zinc was measured and a Vmax of 4.5 nmoles Zn transported per h/g dry wt. The Km for medium Zn increases when the size of the internal erythrocytic Zn pool is augmented, whereas Vmax remains virtually unchanged. A model to explain this phenomenon is proposed. It is suggested that this phenomenon could underlie observations, confirmed here, that the in vitro uptake of Zn by animal erythrocytes depends on the Zn status of the animal.

Laboratory assessment of early dietary, subclinical zinc deficiency: a model study on weaning rats

Male weaning rats were pair-fed a low-zinc diet or a control diet. After 10 d, the animals fed the low-zinc diet showed physiologic signs of deficiency; however, they showed no clinical symptoms. Their estimated whole body zinc was 25 mumol versus 39 mumol for the controls. The 65Zn absorption increased 2-fold and the tissue distribution altered: muscle and erythrocytes contained more, small intestine and liver less activity at 0.5 h postdose. In vitro, the erythrocyte 65Zn uptake rate increased also. The 65Zn uptake experiments required small quantities of erythrocytes. The difference observed between the deficient and control cells was significant and showed little overlap. The increase of the 65Zn uptake from a medium was not affected when the animals underwent endotoxin exposure 24 h before, as was reported to occur in whole blood 65Zn uptake. Therefore, we suggest the in vitro erythrocyte 65Zn uptake, performed in a standardized, near physiologic medium, to detect early, subclinical zinc deficiency.

Discrimination between low dietary zinc and endotoxin exposure: a model study on weaning rats

To establish a parameter for zinc status that is independent of the occurrence of infection, we studied the effects of low dietary zinc and endotoxin in weaning rats 21 d after 65Zn intubation. We monitored aspects of zinc status (tissue zinc content, 65Zn distribution, and specific 65Zn activity in tissue) and 65Zn metabolism (absorption, excretion, and biologic half-life), as well as weight gain, feed conversion, and dietary zinc use. The low zinc diet induced classical deficiency with losses of bone zinc, resulting in lower content (7.4 versus 19.6 mumol) and higher spec act (17 versus 8 kBq/mumol). Other tissue-specific and plasma-specific activities were also higher (overall, 20 versus 8 kBq/mumol; plasma, 8 versus 4 kBq/mumol). Endotoxin caused lower total-plasma zinc (0.04 versus 0.05 mumol) but did not affect spec act (4 kBq/mumol); combined endotoxin and low-zinc diet caused low total-plasma zinc (0.01 mumol) and high spec act, as did the low-zinc diet alone (12 kBq/mumol). We conclude that plasma-spec act (or stable isotope enrichment) can serve as an index for nutritional zinc status during recurrent infection.

In vitro exchangeable erythrocytic zinc

Exchangeable erythrocytic zinc is measured by 65Zn uptake in and release from erythrocytes under standardized and near, physiological conditions: 7.6 microM zinc and 580 microM albumin in the medium. The intracellular exchangeable erythrocytic zinc pool in healthy volunteers amounts to 5 mumol zinc/L packed cells. The half-time of the exchange is 7 h, its activation energy 84 kJ/mol. The effects of the variation in temperature and the concentrations of albumin, as well as the effects of some zinc carriers, cell transport inhibitors, and stress hormones on the 65Zn uptake are measured.

Clinical examination of weanling rats with early zinc deficiency

In order to gain experience about the detection of adverse effects during a scientific procedure, we carried out a clinical examination of rats with zinc deficiency. In weanling rats fed a zinc-deficient diet (30 mumol zinc/kg) for 10 days, the mean tibial concentration of zinc was reduced by 53% and body weight gain by 73% when compared with rats fed a diet containing an adequate amount of zinc (150 mumol zinc/kg). In a small open field on day 9 of the experiment, the deficient rats more frequently displayed the posture standing upright with elevated heels. On day 10 of the experiment a clinical examination was carried out at random and 'blind' by three independent assessors. Out of 20 variables scored quantitatively on each individual animal, only body size differed between normal and deficient rats. Other classical signs of zinc deficiency, such as alopecia, dermatitis and diarrhoea, were not detected. It is concluded that in this rat model of zinc deficiency, no evidence for extreme discomfort can be demonstrated.