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Because (i). endothelial cells are important players in cardiovascular diseases and (ii). Mg deficiency promotes atherosclerosis, thrombosis and hypertension, we evaluated whether low concentrations of Mg could directly affect endothelial behavior. We found that low Mg concentrations reversibly inhibit endothelial proliferation, and this event correlates with a marked down-regulation of the levels of CDC25B. The inhibition of endothelial proliferation is due to an up-regulation of interleukin-1 (IL-1), since an antisense oligonucleotide against IL-1 could prevent the growth inhibition observed in cells exposed to low concentrations of the cation. We also report the up-regulation of Vascular Cell Adhesion Molecule-1 (VCAM) and Plasminogen Activator Inhibitor (PAI)-1 after Mg deficiency. VCAM is responsible, at least in part, of the increased adhesion of monocytoid U937 cells to the endothelial cells grown in low magnesium. In addition, endothelial migratory response is severely impaired. By cDNA array, we identified several transcripts modulated by exposure to low Mg, some of which-c-src, ezrin, CD9, cytohesin and zyxin-contribute to endothelial adhesion to substrates and migration. In conclusion, our results demonstrate a direct role of low magnesium in promoting endothelial dysfunction by generating a pro-inflammatory, pro-thrombotic and pro-atherogenic environment that could play a role in the pathogenesis cardiovascular disease.

Resistant starch and inulin are complex carbohydrates that are fermented by the microflora and known to increase colonic absorption of minerals in animals. The fermentation of these substrates in the large bowel to short-chain fatty acids is the main reason for this increase in mineral absorption. The purpose of the present study was to examine the potential synergistic effect of a combination of these two fermentable carbohydrates. For this purpose, thirty-two adult male Wistar rats weighing 200 g were used in the present study. The rats were distributed into four groups, and fed for 21 d a fibre-free basal purified diet or diet containing 100 g inulin, or 150 g resistant starch (raw potato starch)/kg diet or a blend of 50 g inulin and 75 g resistant starch/kg diet. After an adaptation period of 14 d, the rats were then transferred to metabolic cages and dietary intake, faeces and urine were monitored for 5 d. The animals were then anaesthetized and caecal Ca and Mg absorption were measured. Finally, the rats were killed and blood, caecum and tissues were sampled. Ca and Mg levels were assessed in diets, faeces, urine, caecum and plasma by atomic absorption spectrometry. Our results confirmed that inulin and resistant starch ingestion led to considerable caecal fermentation in the three experimental groups compared with the control group diet. Moreover, both carbohydrates significantly increased the intestinal absorption and balance of Ca and Mg, without altering the plasma level of these two minerals. Interestingly, the combination of the studied carbohydrates increased significantly ðP , 0 : 05Þ the caecal soluble Ca and Mg concentrations, the apparent intestinal absorption and balance of Ca, and non-significantly the plasma Mg level. In conclusion, a combination of different carbohydrates showed synergistic effects on intestinal Ca absorption and balance in rats. Further studies with other types of carbohydrate combinations should be carried out to extend these findings.

Recent findings indicate that in addition to its hyperlipemic effect, a high fructose diet has a pro-oxidant effect in rats compared with a starch-based diet. Oligofructose (OFS) has already been shown to decrease plasma lipids in rats. We assessed the impact of fructose on oxidative stress by supplementing a high fructose diet with OFS. Rats were fed either a high fructose diet or a starch-based diet, with or without supplementation of 10 g/100 g oligofructose for 4 wk. Regardless of the type of carbohydrate, OFS in the diet produced an enlargement of the cecum and led to a significant increase in the SCFA cecum pool. Fructose feeding was associated with significantly higher insulin plasma concentrations (+63%) in the control groups, whereas insulin plasma concentrations did not differ in rats fed the fructose diet supplemented with OFS. Plasma leptin concentration was significantly lower (approximately 50%) in the OFS-supplemented fructose group compared with the other three groups. Fructose feeding in rats also significantly increased plasma (P < 0.001) and liver (P < 0.001) triglyceride (TG) concentrations and the addition of OFS prevented the TG accumulation induced by fructose in the liver (P < 0.05) and hyperlipemia (P < 0.05). OFS consumption prevented (P < 0.05) the lower plasma vitamin E/TG ratio in rats fed the fructose diet. Control rats fed the fructose diet had high plasma TBARS values compared with rats fed the starch diet, whereas TBARS values remained unchanged when rats were supplemented with OFS. Control rats fed the fructose diet had higher TBARS urine values and higher heart tissue susceptibility to peroxidation compared with rats fed the starch diet, and this effect was significantly reduced by OFS consumption. Further studies are required to identify the mechanisms underlying the protective effect of OFS against the pro-oxidant effect of fructose. However, the potential nutritional benefits of OFS supplementation in fructose-rich diets are suggested.

There is overwhelming evidence that dietary fibers are an important component of human and animal diets and play an important role in human health. Because dietary fibers and some associated substances, such as phytate, have in vitro mineral-binding capacities, they have been thought to impair absorption of minerals such as calcium, iron and zinc, although magnesium absorption seems to be less affected. Indeed, the effect of dietary fibers depends largely on their own nature and characteristics, and also on mineral homeostasis. In 1977 it was observed that resistant starch, a fermentable dietary fiber, could improve Mg absorption in rats. More recently, attention has been focused on other fermentable substrates such as inulin and oligo- or polysaccharides, for their potential prebiotic and health effects. Studies conducted on different types of fermentable carbohydrates have confirmed their beneficial effect on Mg absorption in different animal species. The majority of these studies have also sought to determine the effects of fibers on other minerals such as calcium, iron and zinc. In contrast to the studies with Mg, these studies did not show a consistent effect on the absorption of these minerals. This is due to the particularities of sites and mechanism of Mg absorption. To date, four human studies have been carried out that generally confirmed the enhancing effect of fermentable oligo- or polysaccharides on Mg absorption.

The different types of fructans studied in the present experiment seem to have similar activity on mineral absorption. However, the combination of OF and HP-inulin showed synergistic effects on intestinal Ca absorption and balance in rats. Further studies with other combinations of fructans need to be done to extend these findings.

Recent findings indicate that a high fructose diet has a prooxidant effect in rats compared with a starch diet. Because honey is rich in fructose, the aim of this study was to assess the effect of substituting honey for refined carbohydrates on lipid metabolism and oxidative stress. Rats were fed for 2 wk purified diets containing 65 g/100 g carbohydrates as wheat starch or a combination of fructose and glucose or a honey-based diet prepared by substituting honey for refined carbohydrates (n = 9/group). The same amount of fructose was provided by the honey and fructose diets. The hypertriglyceridemic effect of fructose was not observed when fructose was provided by honey. Compared with those fed starch, fructose-fed rats had a lower plasma alpha-tocopherol level, higher plasma nitrite and nitrate (NOx) levels and were less protected from lipid peroxidation as indicated by heart homogenate TBARS concentration. Compared with those fed fructose, honey-fed rats had a higher plasma alpha-tocopherol level, a higher alpha-tocopherol/triacylglycerol ratio, lower plasma NOx concentrations and a lower susceptibility of heart to lipid peroxidation. Further studies are required to identify the mechanism underlying the antioxidant effect of honey but the data suggest a potential nutritional benefit of substituting honey for fructose in the diet.