Dietary phytosterols and phytostanols decrease cholesterol levels but increase blood pressure in WKY inbred rats in the absence of salt-loading

<p>Abstract</p> <p>Background</p> <p>There are safety concerns regarding widespread consumption of phytosterol and phytostanol supplemented food products. The aim of this study was to determine, in the absence of excess dietary salt, the individual effects of excess accumulation of dietary phytosterols and phytostanols on blood pressure in Wistar Kyoto (WKY) <it>inbred </it>rats that have a mutation in the <it>Abcg5 </it>gene and thus over absorb phytosterols and phytostanols.</p> <p>Methods</p> <p>Thirty 35-day old male WKY <it>inbred </it>rats (10/group) were fed a control diet or a diet containing phytosterols or phytostanols (2.0 g/kg diet) for 5 weeks. The sterol composition of the diets, plasma and tissues were analysed by gas chromatography. Blood pressure was measured by the tail cuff method. mRNA levels of several renal blood pressure regulatory genes were measured by real-time quantitative PCR.</p> <p>Results</p> <p>Compared to the control diet, the phytosterol diet resulted in 3- to 4-fold increases in the levels of phytosterols in plasma, red blood cells, liver, aorta and kidney of WKY <it>inbred </it>rats (<it>P </it>< 0.05). The phytostanol diet dramatically increased (> 9-fold) the levels of phytostanols in plasma, red blood cells, liver, aorta and kidney of these rats (<it>P </it>< 0.05). The phytosterol diet decreased cholesterol levels by 40%, 31%, and 19% in liver, aorta and kidney, respectively (<it>P </it>< 0.05). The phytostanol diet decreased cholesterol levels by 15%, 16%, 20% and 14% in plasma, liver, aorta and kidney, respectively (<it>P </it>< 0.05). The phytostanol diet also decreased phytosterol levels by 29% to 54% in plasma and tissues (<it>P </it>< 0.05). Both the phytosterol and phytostanol diets produced significant decreases in the ratios of cholesterol to phytosterols and phytostanols in plasma, red blood cells, liver, aorta and kidney. Rats that consumed the phytosterol or phytostanol diets displayed significant increases in systolic and diastolic blood pressure compared to rats that consumed the control diet (<it>P </it>< 0.05). The phytosterol diet increased renal <it>angiotensinogen </it>mRNA levels of these rats.</p> <p>Conclusion</p> <p>These data suggest that excessive accumulation of dietary phytosterols and phytostanols in plasma and tissues may contribute to the increased blood pressure in WKY <it>inbred </it>rats in the absence of excess dietary salt. Therefore, even though phytosterols and phytostanols lower cholesterol levels, prospective clinical studies testing the net beneficial effects of dietary phytosterols and phytostanols on cardiovascular events for subgroups of individuals that have an increased incorporation of these substances are needed.</p

Regulation of leukotriene biosynthesis in eosinophilic and neutrophilic HL-60 cells

Leukotrienes are potent mediators of immediate hypersensitivity reactions and are predominantly produced by myeloid cells. Although the regulatory mechanisms governing leukotriene biosynthesis are largely unknown, cytokines have been shown to upregulate leukotriene production by these cells. GM-CSF primed leukotriene biosynthesis in a dose-dependent manner in eosinophilic HL-60 cells, whereas IL-5 had no effect on leukotriene production in this cell line. GM-CSF did not affect the kinetic parameters of LTC4 synthase and therefore most likely enhanced the rate of leukotriene biosynthesis by acting upstream of this catalytic event in the biosynthetic pathway. This differential priming ability was not merely due to different receptor populations or differences in the affinity and stability of the ligand-receptor complexes of GM-CSF and IL-5. Receptor binding assays and phosphotyrosine patterns demonstrated that IL-5 is incapable of signal transduction in eosinophilic HL-60 cells, despite the fact that both GM-CSF and IL-5 receptors share a common beta-chain component, necessary for high-affinity ligand binding and signal transduction. The regulation mechanisms that govern leukotriene biosynthesis during myeloid cell differentiation to eosinophils or neutrophils were revealed to be analogous up to the point where the leukotriene biosynthetic pathway diverges. At the stage In the leukotriene biosynthetic pathway where LTA4 can be converted to either LTB 4 or LTC4, specific regulators of transcription may become activated as a myelocyte differentiates. LTA4 hydrolase expression was shown to be up-regulated in neutrophlis whereas the activity and protein and messenger RNA expression of LTC4 synthase were up-regulated in eosinophils. Microsomal GST-II is a novel membrane bound enzyme that possesses LTC4 synthesizing activity and consequently may also be responsible for regulating the formation of LTC4. Microsomal GST-II was determined to be the predominant enzyme respon

Antioxidant Supplements Improve Profiles of Hepatic Oxysterols and Plasma Lipids in Butter-fed Hamsters

Hypercholesterolemia diets are associated with oxidative stress that may contribute to hypercholesterolemia by adversely affecting enzymatically-generated oxysterols involved in cholesterol homeostasis. An experiment was conducted to examine whether the cholesterol-lowering effects of the antioxidants selenium and α-tocopherol were related to hepatic oxysterol concentrations. Four groups of male Syrian hamsters (n = 7-8) were fed high cholesterol and saturated fat (0.46% cholesterol, 14.3% fat) hypercholesterolemic semi-purified diets: 1) Control; 2) Control + α-tocopherol (67 IU all-racemic-α-tocopheryl-acetate/kg diet); 3) Control + selenium (3.4 mg selenate/kg diet); and 4) Control + α-tocopherol + selenium. Antioxidant supplementation was associated with lowered plasma cholesterol concentrations, decreased tissue lipid peroxidation and higher hepatic oxysterol concentrations. A second experiment examined the effect of graded selenium doses (0.15, 0.85, 1.7 and 3.4 mg selenate/kg diet) on mRNA expression of the oxysterol-generating enzyme, hepatic 27-hydroxylase (CYP27A1, EC 1.14.13.15), in hamsters (n = 8-9) fed the hypercholesterolemic diets. Supplementation of selenium at 3.4 mg selenate/kg diet was not associated with increased hepatic 27-hydroxylase mRNA. In conclusion, the cholesterol lowering effects of selenium and α-tocopherol were associated with increased hepatic enzymatically generated oxysterol concentrations, which appears to be mediated via improved antioxidant status rather than increased enzymatic production

Bisphenol A induces DSB-ATM-p53 signaling leading to cell cycle arrest, senescence, autophagy, stress response, and estrogen release in human fetal lung fibroblasts

Experimental and/or epidemiological studies suggest that prenatal exposure to bisphenol A (BPA) may delay fetal lung development and maturation and increase the susceptibility to childhood respiratory disease. However, the underlying mechanisms remain to be elucidated. In our previous study with cultured human fetal lung fibroblasts (HFLF), we demonstrated that 24-h exposure to 1 and 100 µM BPA increased GPR30 protein in the nuclear fraction. Exposure to 100 μM BPA had no effects on cell viability, but increased cytoplasmic expression of ERβ and release of GDF-15, as well as decreased release of IL-6, ET-1, and IP-10 through suppression of NFκB phosphorylation. By performing global gene expression and pathway analysis in this study, we identified molecular pathways, gene networks, and key molecules that were affected by 100, but not 0.01 and 1 µM BPA in HFLF. Using multiple genomic and proteomic tools, we confirmed these changes at both gene and protein levels. Our data suggest that 100 μM BPA increased CYP1B1 and HSD17B14 gene and protein expression and release of endogenous estradiol, which was associated with increased ROS production and DNA double-strand breaks, upregulation of genes and/or proteins in steroid synthesis and metabolism, and activation of Nrf2-regulated stress response pathways. In addition, BPA activated ATM-p53 signaling pathway, resulting in increased cell cycle arrest at G1 phase, senescence and autophagy, and decreased cell proliferation in HFLF. The results suggest that prenatal exposure to BPA at certain concentrations may affect fetal lung development and maturation, and thereby affecting susceptibility to childhood respiratory diseases