silicon and Atherosclerosis

Silicon is the second most abundant element in nature behind oxygen. As a metalloid, silicon has been used in many industrial applications including use as an additive in the food and beverage industry. As a result, humans come into contact with silicon through both environmental exposures but also as a dietary component. Moreover, many forms of silicon, that is, Si bound to oxygen, are water-soluble, absorbable, and potentially bioavailable to humans presumably with biological activity. However, the specific biochemical or physiological functions of silicon, if any, are largely unknown although generally thought to exist. As a result, there is growing interest in the potential therapeutic effects of water-soluble silica on human health. For example, silicon has been suggested to exhibit roles in the structural integrity of nails, hair, and skin, overall collagen synthesis, bone mineralization, and bone health and reduced metal accumulation in Alzheimer's disease, immune system health, and reduction of the risk for atherosclerosis. Although emerging research is promising, much additional, corroborative research is needed particularly regarding speciation of health-promoting forms of silicon and its relative bioavailability. Orthosilicic acid is the major form of bioavailable silicon whereas thin fibrous crystalline asbestos is a health hazard promoting asbestosis and significant impairment of lung function and increased cancer risk. It has been proposed that relatively insoluble forms of silica can also release small but meaningful quantities of silicon into biological compartments. For example, colloidal silicic acid, silica gel, and zeolites, although relatively insoluble in water, can increase concentrations of water-soluble silica and are thought to rely on specific structural physicochemical characteristics. Collectively, the food supply contributes enough silicon in the forms aforementioned that could be absorbed and significantly improve overall human health despite the negative perception of silica as a health hazard. This review discusses the possible biological potential of the metalloid silicon as bioavailable orthosilicic acid and the potential beneficial effects on human health.

Topics: Alzheimer Disease; Animals; Atherosclerosis; Humans; Silicon; Silicon Dioxide

Although cohort studies of the health effects of PM2.5 have developed exposure prediction models to represent spatial variability across participant residences, few models exist for PM2.5 components. We aimed to develop a city-specific spatio-temporal prediction approach to estimate long-term average concentrations of four PM2.5 components including sulfur, silicon, and elemental and organic carbon for the Multi-Ethnic Study of Atherosclerosis cohort, and to compare predictions to those from a national spatial model. Using 2-week average measurements from a cohort-focused monitoring campaign, the spatio-temporal model employed selected geographic covariates in a universal kriging framework with the data-driven temporal trend. Relying on long-term means of daily measurements from regulatory monitoring networks, the national spatial model employed dimension-reduced predictors using universal kriging. For the spatio-temporal model, the cross-validated and temporally-adjusted R(2) was relatively higher for EC and OC, and in the Los Angeles and Baltimore areas. The cross-validated R(2)s for both models across the six areas were reasonably high for all components except silicon. Predicted long-term concentrations at participant homes from the two models were generally highly correlated across cities but poorly correlated within cities. The spatio-temporal model may be preferred for city-specific health analyses, whereas both models could be used for multi-city studies.

Topics: Air Pollutants; Air Pollution; Atherosclerosis; Carbon; Cities; Cohort Studies; Environmental Exposure; Environmental Monitoring; Ethnicity; Humans; Particle Size; Particulate Matter; Reproducibility of Results; Silicon; Spatio-Temporal Analysis; Sulfur; United States

Surface bioconjugation of biomolecules has gained enormous attention for developing advanced biomaterials including biosensors. While conventional immobilization (by physisorption or covalent couplings using the functional groups of the endogenous amino acids) usually results in surfaces with low activity, reproducibility and reusability, the application of methods that allow for a covalent and uniformly oriented coupling can circumvent these limitations. In this study, the nanobody targeting Vascular Cell Adhesion Molecule-1 (NbVCAM1), an atherosclerotic biomarker, is engineered with a C-terminal alkyne function via Expressed Protein Ligation (EPL). Conjugation of this nanobody to azidified silicon wafers and Biacore™ C1 sensor chips is achieved via Copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) "click" chemistry to detect VCAM1 binding via ellipsometry and surface plasmon resonance (SPR), respectively. The resulting surfaces, covered with uniformly oriented nanobodies, clearly show an increased antigen binding affinity, sensitivity, detection limit, quantitation limit and reusability as compared to surfaces prepared by random conjugation. These findings demonstrate the added value of a combined EPL and CuAAC approach as it results in strong control over the surface orientation of the nanobodies and an improved detecting power of their targets-a must for the development of advanced miniaturized, multi-biomarker biosensor platforms.

Topics: Antigens; Atherosclerosis; Biomarkers; Biosensing Techniques; Buffers; Humans; Protein Binding; Silicon; Single-Domain Antibodies; Surface Plasmon Resonance; Vascular Cell Adhesion Molecule-1

Dietary silicon has been positively linked with vascular health and protection against atherosclerotic plaque formation, but the mechanism of action is unclear.. We investigated the effect of dietary silicon on 1) serum and aorta silicon concentrations, 2) the development of aortic lesions and serum lipid concentrations, and 3) the structural and biomechanic properties of the aorta.. Two studies, of the same design, were conducted to address the above objectives. Female mice, lacking the apolipoprotein E (apoE) gene, and therefore susceptible to atherosclerosis, were separated into 3 groups of 10-15 mice, each exposed to a high-fat diet (21% wt milk fat and 1.5% wt cholesterol) but with differing concentrations of dietary silicon, namely: silicon-deprived (-Si; <3-μg silicon/g feed), silicon-replete in feed (+Si-feed; 100-μg silicon/g feed), and silicon-replete in drinking water (+Si-water; 115-μg silicon/mL) for 15-19 wk. Silicon supplementation was in the form of sodium metasilicate (feed) or monomethylsilanetriol (drinking water).. The serum silicon concentration in the -Si group was significantly lower than in the +Si-feed (by up to 78%; P < 0.003) and the +Si-water (by up to 84%; P < 0.006) groups. The aorta silicon concentration was also lower in the -Si group than in the +Si-feed group (by 65%; P = 0.025), but not compared with the +Si-water group. There were no differences in serum and aorta silicon concentrations between the silicon-replete groups. Body weights, tissue wet weights at necropsy, and structural, biomechanic, and morphologic properties of the aorta were not affected by dietary silicon; nor were the development of fatty lesions and serum lipid concentrations.. These findings suggest that dietary silicon has no effect on atherosclerosis development and vascular health in the apoE mouse model of diet-induced atherosclerosis, contrary to the reported findings in the cholesterol-fed rabbit model.

Topics: Animals; Aorta; Apolipoproteins E; Atherosclerosis; Body Weight; Cholesterol, HDL; Cholesterol, LDL; Diet; Diet, High-Fat; Dietary Supplements; Disease Models, Animal; Endothelium, Vascular; Female; Mice; Mice, Inbred C57BL; Mice, Knockout; Plaque, Atherosclerotic; Silicon; Triglycerides

The aim of this study was to investigate the effects of dietary silicon-enriched spirulina (SES) on atherosclerosis.. Hamsters (six per group) on a high-fat (HF) diet received SES or non-enriched spirulina (both at 57 mg/kg body weight) daily. This corresponded to 0.57 mg silicon/kg body weight daily.. The HF diet induced dyslipidemia, insulin resistance, oxidative stress, and vascular dysfunction. Compared with the HF group, SES attenuated increases of lipemia and prevented insulin resistance (IR) (P = 0.001). SES protected against oxidative stress through a reduction of heart (P = 0.006) and liver (P < 0.0001) nicotinamide adenine dinucleotide phosphate-oxidase activity and by sparing the activity of superoxide dismutase (P = 0.0017) and glutathione peroxidase (P = 0.01861). SES decreased inflammation, lowering tumor necrosis factor-α (P = 0.0006) and interleukin-6 levels (P = 0.0112), decreasing polymorphonuclear cells and preventing nuclear factor-κB activity (P = 0.0259). SES corrected plasma level of monocyte chemoattractant protein-1 (P = 0.0380), which was increased by the HF diet. Finally, SES supplementation prevented vascular and endothelial functions assessed respectively by the contractile response to the agonist phenylephrine and the relaxation induced by acetylcholine.. SES protects against metabolic imbalance, inflammation, oxidative stress, and vascular dysfunction induced by an HF diet, and could prevent the atherogenic processes. Synergistic effects between spirulina and silicon were observed.

Topics: Animals; Atherosclerosis; Biomarkers; Cricetinae; Cytokines; Diet, High-Fat; Dietary Supplements; Drug Synergism; Dyslipidemias; Endothelium, Vascular; Glutathione Peroxidase; Heart; Inflammation; Inflammation Mediators; Insulin Resistance; Liver; Male; Oxidative Stress; Silicon; Spirulina; Superoxide Dismutase; Trace Elements

Topics: Arteries; Arteriosclerosis; Atherosclerosis; Humans; Potassium; Silicon