Dominique Bayle

Changes in gene expression in rat thymocytes identified by cDNA array support the occurrence of oxidative stress in early magnesium deficiency.

Magnesium deficiency in experimental animals leads to inflammation, exacerbated immune stress response and a decrease of specific immune response. It also results in a significant increase in free radical species and subsequent tissue injury. An accelerated thymus involution was observed in Mg-deficient rats in relation to enhanced apoptosis and enhanced susceptibility to oxidative stress. To examine the stress-inducing effects of low Mg status on thymocytes, cDNA arrays were used to evaluate changes in gene expression in weaning rats submitted to Mg deficiency of short duration (2 days). Several genes exhibited changes in their expression caused by Mg deficiency before any perceptible modification in cell integrity and functions. The up-regulated genes included cytochrome c oxidase, glutathione transferase, CuZn superoxide dismutase, genes associated with the stress response (HSP70 and HSP84) and a gene involved in DNA synthesis and repair (GADD45). The down-regulated genes included Na/P cotransporter 1. These findings are consistent with altered cell growth, modifications of ion fluxes and oxidative stress described during Mg deficiency. The observation of induction of genes involved in protection and repair in cells from Mg-deficient animals provides additional evidence of the role of oxidative stress in the pathobiology of this deficiency.

Dietary iron regulates hepatic hepcidin 1 and 2 mRNAs in mice

Recently discovered peptide-hepcidin (Hepc) may be a central player in the communication of iron body stores to the intestinal absorptive cells and thus involved in the maintenance of iron homeostasis. The aim of this study was to determine the effects of the level of dietary iron on Hepc gene expression in the liver. OF1 male mice were fed for 3 weeks either control diet (35 mg iron/kg diet), low-iron diet (1 mg iron/kg diet), or high-iron diet (500 mg iron/kg diet), and Hepc 1 and 2 mRNA abundance in the liver was assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). Results clearly showed that Hepc gene expression is upregulated by high dietary iron and downregulated when the dietary iron level is low. Both Hepc 1 and Hepc 2 expression responds coordinately to dietary iron. This work provides additional evidence of the key role of Hepc in the regulation of iron homeostasis.

Effect of selenium deficiency on hepatic lipid and lipoprotein metabolism in the rat

Since experimental Se deficiency results in a significant increase in plasma cholesterol concentration the present investigation was undertaken to assess further the influence of this deficiency on the expression of proteins involved in hepatic lipid metabolism. Se deficiency was induced by feeding weanling male Wistar rats on a deficient diet for 6 weeks. Hypercholesterolaemia associated with Se deficiency was related to increased 3-hydroxy-3-methylglutaryl-coA (HMG-CoA) reductase (EC 1.1.1.34) activity in liver microsomes as compared with control animals. Hepatic lipoprotein receptor levels (LDL-receptor and HDL-binding proteins, HB1 and HB2) were not significantly affected by Se deficiency, as assessed by immunoblotting. Plasma triacylglycerol concentrations tended to decrease in Se-deficient rats in concert with their reduced post-Triton secretion. There was no significant effect of Se deficiency on the hepatic synthesis of apolipoproteins. These results point to the need for further investigations into the mechanism related to the increased activity of HMG-CoA reductase and the enhanced cholesterogenesis in the liver of Se-deficient rats likely to result from this.

Effects of dietary fermentable fiber on fatty acid synthesis and triglyceride secretion in rats fed fructose-based diet : studies with sugar-beet fiber

Abstract In an attempt to elucidate the role of the dietary fermentable fiber in reduction of hyperlipidemia, we substituted 30% wheat starch with 30% sugar-beet fiber in rats fed a fructose-based (41% fructose), low-fat (2% corn oil) diet. Male Wistar rats ate the test diets for 3 weeks. Feeding the sugar-beet fiber (SBF) diet resulted in a significant enlargement of the cecum; it also increased the concentration of volatile fatty acids compared with rats fed a fiber-free (FF) diet. Feeding SBFdecreased plasma triglyceride and cholesterol concentrations in the postprandial as well as the postabsorptive period. In the liver, triglyceride levels were depressed in concert with the decreased liver lipogenesis and the post-Triton triglyceride secretion. Liver cholesterol levels were unaffected by SBF diet feeding. SBF-fed animals were markedly less fat compared with fiber-free-diet-fed rats. Adipose tissue lipogenesis was depressed in the postprandial period in SBF-fed animals. In short, this study suggests that substitution of easily digested carbohydrates by certain fermentable fibers may play an interesting role in the reduction of hyperlipidemia and obesity.

Morphological and immune response alterations in the intestinal mucosa of the mouse after short periods on a low-magnesium diet

The importance of Mg for the immune function is well recognized; however, there is no information available about the effect of Mg intake on the modulation of local immune response in the intestine. Thus, in the present study the hypothesis that short periods of Mg deprivation can affect intestinal mucosa and local immune response was tested. For this purpose, OF1 female mice were fed a semipurified diet (1000 mg Mg/kg diet). For 3 d before immunization and 1 d after, half of the animals were fed a Mg-deficient diet (30 mg Mg/kg diet), three immunizations per os were performed every 3 weeks with Escherichia coli producing the CS31A capsule-like protein (1010 or bacteria per animal). Mice were killed 10 d after the last immunization. The level of specific anti CS31A immunoglobulin (Ig) G and IgA in the serum and secretory IgA in the intestinal secretions and faeces were measured by ELISA. The results indicated that administration of a high dose of immunogen with a low-Mg diet led to lower specific IgA levels in the intestinal mucus and serum. Administration of a low dose of immunogen with a low-Mg diet led to lower IgA and IgG levels in the serum and secretory IgA coproantibodies. To assess alterations of intestinal mucosa caused by a low-Mg diet for a short period, histological and scanning electron microscopy analyses were performed on samples from mice (not submitted to the vaccination protocol) after 3 d on the Mg-deficient diet. These analyses showed several alterations, suggesting perturbations in the growth of the intestinal mucosa. These changes were accompanied by modifications in the expression of several genes involved in cell growth and stress response. From this present work, it may be concluded that short periods of Mg deprivation can affect the intestinal mucosa and local immune response of the intestine.

Effect of zinc supplementation on in vitro copper-induced oxidation of low-density lipoproteins in healthy French subjects aged 55-70 years: the Zenith Study.

Zn has been shown to possess antioxidant properties in vitro and in vivo. As inadequate dietary Zn intake has been reported in these populations, Zn supplementation may protect against oxidative stress and thereby limit the progression of degenerative diseases in such populations. We conducted the present study to evaluate the long-term supplementation effects of two moderate doses of Zn on in vitro Cu-induced LDL oxidation in French men and women. Three groups of sixteen healthy subjects aged 55-70 years from each sex participated in this randomized double-blind, placebo-controlled study. Each group received for six months either 0, 15 or 30 mg supplemental Zn per d. At the beginning and at the end of the supplementation periods, dietary intakes of Zn, Cu, Fe and vitamin E were estimated using 4 d food-intake records (including the weekend) and the GENI program. Zn, Cu, Fe and vitamin E status were also determined. In vitro LDL oxidizability (basal conjugated diene level, maximal conjugated diene formation and lag time) and lipid parameters were also determined. Dietary intakes of Zn, Cu, Fe and vitamin E were adequate in this population. Zn supplementation significantly increased serum Zn levels but did not significantly modify Cu, Fe or vitamin E status. However, Zn supplementation had no effect on in vitro LDL oxidation parameters, nor were there any sex-related differences in in vitro LDL oxidizability. The present study showed that long-term Zn supplementation of healthy subjects aged 55-70 years had no effect on in vitro Cu-induced LDL oxidation under the study conditions.

Response of diamine oxidase and other plasma copper biomarkers to various dietary copper intakes in the rat and evaluation of copper absorption with a stable isotope

There is a lack of agreement on index of Cu status and reliable and sensitive biomarkers are still required. The purpose of this present work was to assess in rats the sensitivity of diamine oxidase (DAO) activity, a recently proposed biomarker, to modifications in dietary Cu intake in comparison with other plasma biomarkers of Cu status. We also evaluated the effect of Cu dietary level on Cu and Zn intestinal absorption. Results showed that plasma Cu and plasma caeruloplasmin were significantly decreased at day 8 compared with the control group (7.4 mg Cu/kg diet) while DAO activity was significantly decreased at day 12 of the deficient diet (0.61 mg Cu/kg diet). Cu supplementation (35 mg Cu/kg diet) had no effect on any of the studied biomarkers of Cu status. In Cu-deficient rats plasma Cu and DAO activities were normalized 4 d after return to the control diet while caeruloplasmin was normalized later, at day 11. Apparent absorption values (%) of total Cu or 65Cu isotope were significantly increased in the Cu-deficient rats compared with the other groups and similar in the control and the Cu-supplemented groups. The urinary excretion of total Cu or 65Cu isotope were increased in the Cu-supplemented group compared with the other two groups. Both apparent absorption and urinary excretion of total Zn or 67Zn isotope remained unchanged in the three experimental groups. In conclusion, DAO activity seemed to be less sensitive to Cu deficiency than plasma Cu or caeruloplasmin concentrations. The present study also showed a significant increase in Cu intestinal absorption with dietary Cu restriction but no decrease with Cu supplementation in the rat.

Apolipoprotein B gene expression in rat intestine The effect of dietary fiber

The effect of the dietary fiber on apo B mRNA level was studied in the intestine of rats that were fed either fiber‐free or high‐fiber (30% sugar‐beet fiber) low‐fat diets for 3 weeks. The fiber diet studied does not affect jejunal apo B mRNA levels but decreases the level of ileal apo B mRNA. In the rat cecum, in both fiber‐free and fiber groups, we failed to detect the apo B mRNA. The test fiber diet feeding markedly increased fecal bile salt and cholesterol excretions. We suggest that dietary fiber can modify apo B expression in the intestine. The increased fecal bile salt excretion might be involved in such a modification.

DHA-derived oxylipins, neuroprostanes and protectins, differentially and dose-dependently modulate the inflammatory response in human macrophages: Putative mechanisms through PPAR activation

ABSTRACT Whereas the anti‐inflammatory properties and mechanisms of action of long chain ω3 PUFAs have been abundantly investigated, research gaps remain regarding the respective contribution and mechanisms of action of their oxygenated metabolites collectively known as oxylipins. We conducted a dose‐dependent and comparative study in human primary macrophages aiming to compare the anti‐inflammatory activity of two types of DHA‐derived oxylipins including the well‐described protectins (NPD1 and PDX), formed through lipoxygenase pathway and the neuroprostanes (14‐A4t‐ and 4‐F4t‐NeuroP) formed through free‐radical mediated oxygenation and expected to be new anti‐inflammatory mediators. Considering the potential ability of these DHA‐derived oxylipins to bind PPARs and knowing the central role of these transcription factors in the regulation of macrophage inflammatory response, we performed transactivation assays to compare the ability of protectins and neuroprostanes to activate PPARs. All molecules significantly reduced mRNA levels of cytokines such as IL‐6 and TNF‐&agr;, however not at the same doses. NPD1 showed the most effect at 0.1 &mgr;M (−14.9%, p<0.05 for IL‐6 and −26.7%, p<0.05 for TNF‐&agr;) while the three other molecules had greater effects at 10 &mgr;M, with the strongest result due to the cyclopentenone neuroprostane, 14‐A4t‐NeuroP (−49.8%, p<0.001 and −40.8%, p<0.001, respectively). Part of the anti‐inflammatory properties of the DHA‐derived oxylipins investigated could be linked to their activation of PPARs. Indeed, all tested oxylipins significantly activated PPAR&ggr;, with 14‐A4t‐NeuroP leading to the strongest activation, and NPD1 and PDX also activated PPAR&agr;. In conclusion, our results show that neuroprostanes and more especially cyclopentenone neuroprostanes have potent anti‐inflammatory activities similar or even more pronounced than protectins supporting that neuroprostanes should be considered as important contributors to the anti‐inflammatory effects of DHA. Graphical abstract Figure. No Caption Available. HighlightsBoth Neuroprostanes and Protectins attenuate inflammatory response of macrophages.Cyclopentenone neuroprostanes have the most potent anti‐inflammatory properties.Protectin D1 is active at low dose and loses its bioactivity at high dose.Neuroprostanes and Protectins might act through PPAR activation.Neuroprostanes preferentially activate PPAR&ggr; while Protectins mainly activate PPAR&agr;.

Hypoalbuminaemia in acute phase response is not related to depressed albumin synthesis: experimental evidence in magnesium-deficient rat

Studies conducted on laboratory animals have clearly established that dietary magnesium (Mg) deficiency leads to aninflammatory process, that might participate in pathological consequences of this deficiency. Several alterations in plasma biochemistry have been described in Mg-deficient animals and the pattern appears to relate to the inflammatory acute phase response. The present study provides experimental evidence that acute phase response caused by Mg deficiency in the rat leads to hypoalbuminaemia. Thus underlying mechanism for the observed hypoalbuminaemia in Mg-deficient rats was studied in the present work. Our results show that total protein and albumin syntheses in the liver were not affected by Mg-deficiency. Because the capacity of the liver to synthesize albumin appears to be maintained the observed hypoalbuminaemia could be due to an increase in catabolism or the escape of this protein from the plasma pool in to the extra-vascular space.