Emerging Evidence on Neutrophil Motility Supporting Its Usefulness to Define Vitamin C Intake Requirements.

Establishing intake recommendations for vitamin C remains a challenge, as no suitable functional parameter has yet been agreed upon. In this report, we review the emerging evidence on neutrophil motility as a possible marker of vitamin C requirements and put the results in perspective with other approaches. A recent in vitro study showed that adequate levels of vitamin C were needed for this function to work optimally when measured as chemotaxis and chemokinesis. In a human study, neutrophil motility was optimal at intakes ≥250 mg/day. Interestingly, a Cochrane review showed a significant reduction in the duration of episodes of common cold with regular vitamin C intakes in a similar range. Additionally, it was shown that at a plasma level of 75 µmol/L, which is reached with vitamin C intakes ≥200 mg/day, incidences of cardiovascular disease were lowest. This evidence would suggest that daily intakes of 200 mg vitamin C might be advisable for the general adult population, which can be achieved by means of a diverse diet. However, additional studies are warranted to investigate the usefulness of neutrophil motility as a marker of vitamin C requirements.

The natural compound ascorbigen modulates NADPH-quinone oxidoreductase (NQO1) mRNA and enzyme activity levels in cultured liver cells and in laboratory rats.

Ascorbigen (ABG) is a natural compound that represents a breakdown product of the glucosinolates that are present in Brassica vegetables. It is postulated that ABG may have anticarcinogenic activity; however, the underlying molecular and cellular mechanisms are largely unknown. In the present study we investigated the effect of ABG on the mRNA and enzyme activity levels of NADPH-quinone oxidoreductase (NQO1), which is centrally involved in the detoxification of xenobiotics, in cultured liver cells and in rats. The mRNA levels of NQO1 showed an increase of up to 100% in cultured liver cells (HepG2) following incubation with different concentrations of ABG (3-100 micromol/l) compared to control cells. Furthermore, NQO1 activity was elevated (up to 20%) by ABG treatment. The in vitro results were confirmed in rats who received either 5 mg/day ABG or vehicle for 7 days. Significantly higher mRNA (a 90% increase) and enzyme activity levels (a 40% increase) of NQO1 were detected in the liver of ABG-treated rats as compared to control animals. Current data indicate that ABG is a moderate inducer of the phase II enzyme NQO1, both in cultured hepatocytes and in vivo.

CMO1 deficiency abolishes vitamin A production from beta-carotene and alters lipid metabolism in mice.

Carotenoids are currently investigated regarding their potential to lower the risk of chronic disease and to combat vitamin A deficiency in humans. These plant-derived compounds must be cleaved and metabolically converted by intrinsic carotenoid oxygenases to support the panoply of vitamin A-dependent physiological processes. Two different carotenoid-cleaving enzymes were identified in mammals, the classical carotenoid-15,15'-oxygenase (CMO1) and a putative carotenoid-9',10'-oxygenase (CMO2). To analyze the role of CMO1 in mammalian physiology, here we disrupted the corresponding gene by targeted homologous recombination in mice. On a diet providing beta-carotene as major vitamin A precursor, vitamin A levels fell dramatically in several tissues examined. Instead, this mouse mutant accumulated the provitamin in large quantities (e.g. as seen by an orange coloring of adipose tissues). Besides impairments in beta-carotene metabolism, CMO1 deficiency more generally interfered with lipid homeostasis. Even on a vitamin A-sufficient chow, CMO1(-/-) mice developed a fatty liver and displayed altered serum lipid levels with elevated serum unesterified fatty acids. Additionally, this mouse mutant was more susceptible to high fat diet-induced impairments in fatty acid metabolism. Quantitative reverse transcription-PCR analysis revealed that the expression of peroxisome proliferator-activated receptor gamma-regulated marker genes related to adipogenesis was elevated in visceral adipose tissues. Thus, our study identifies CMO1 as the key enzyme for vitamin A production and provides evidence for a role of carotenoids as more general regulators of lipid metabolism.

TEAVIGO (epigallocatechin gallate) supplementation prevents obesity in rodents by reducing adipose tissue mass.

BACKGROUND: This study investigated the antiobesity effects of TEAVIGO, a product providing the most abundant green tea catechin, epigallocatechin gallate (EGCG), in a pure form. Two models of diet-induced obesity and an in vitro adipocyte differentiation assay were employed. METHODS: Prevention and regression of diet-induced obesity by dietary supplementation with EGCG was studied in C57BL/6J mice and Sprague-Dawley rats, respectively. Expression of genes regulating lipid metabolism was assessed in adipose tissue. The effects of EGCG on adipocyte differentiation were investigated in vitro. RESULTS: In C57BL/6J mice, EGCG supplementation prevented diet-induced increases in body weight and in fed state plasma levels of glucose, triglycerides, and leptin. EGCG decreased subcutaneous and epididymal adipose tissue weights. Supplementation of EGCG reversed the established obesity in Sprague-Dawley rats. Fatty acid synthase and acetyl-CoA carboxylase-1 mRNA levels were markedly decreased in adipose tissue of EGCG-supplemented mice. EGCG dose dependently inhibited adipocyte differentiation in vitro. CONCLUSION: This study shows for the first time that supplementation with the most abundant green tea polyphenol, EGCG, abolishes diet-induced obesity. This effect is at least partly mediated via a direct influence on adipose tissue. Thus, dietary supplementation with EGCG should be considered as a valuable natural treatment option for obesity.

Effect of EGCG on lipid absorption and plasma lipid levels in rats.

Catechins, compounds derived from green tea, have been shown to reduce plasma cholesterol levels and the rate of cholesterol absorption. We investigated the dose response and the mechanism of action of epigallocatechin gallate (EGCG) on these parameters in rats. Wistar rats were fed a diet high in cholesterol and fat containing either none, 0.25% (0.2 g/day/kg BW), 0.5% (0.4 g/day/kg/BW) or 1.0% (0.7 g/day/kg BW) of EGCG. After 4 weeks of treatment, total cholesterol and low density lipoprotein plasma levels were significantly reduced in the group fed 1% EGCG when compared to the no treatment group. Plasma triglycerides and high-density lipoprotein levels did not change significantly. Following a single oral application of a liquid test-meal, intestinal cholesterol absorption in Wistar rats was 79.3% in the control group. In the group treated with 0.1 g/kg BW EGCG intestinal cholesterol absorption decreased to 73.7% and in the group treated with 0.5 g/kg BW of EGCG intestinal cholesterol absorption fell significantly to 62.7% (P = 0.005). Total fat absorption was very efficient in the control group (99.5% of the applied dose) and decreased significantly but moderately in the group treated with the highest doses of EGCG (0.75, 1 g/kg BW). In an in-vitro biliary micelle model, the addition of 55 microM to 1300 microM EGCG not only decreased cholesterol solubility dose-dependently in these micelles but also altered the size of the mixed lecithin/taurocholate/cholesterol micelles as demonstrated by light scattering. This study provides evidence suggesting that the cholesterol-lowering effect of green tea is mainly elicited by EGCG, one of the most abundant catechins contained in green tea. It is suggested that one of the underlying mechanisms by which EGCG affects lipid metabolism is by interfering with the micellar solubilization of cholesterol in the digestive tract, which then in turn decreased cholesterol absorption.