Soluble silica and coral sand suppress high blood pressure and improve the related aortic gene expressions in spontaneously hypertensive rats

Benefits of Dietary Supplementation with Specific Silicon-Enriched Spirulina on Arterial Function in Healthy Elderly Individuals: A Randomized, Placebo-Controlled Trial

Background/Objectives: Vascular aging is associated with increased arterial stiffness and changes in the wall structure, leading to a loss of elasticity. Silicon is abundant in arteries and plays a key role in the synthesis and stabilization of elastin fibers. In animal models of accelerated cardiovascular aging, a specific nutritional supplement based on silicon-enriched spirulina (SpSi) has been shown to have beneficial effects on vascular function. The present study, designed as a randomized, double-blind, placebo-controlled trial, aimed to evaluate the effectiveness of this SpSi supplement on aging-related changes in vascular function among healthy older adults. Methods: Here, 120 healthy volunteers aged 60-75 years were enrolled and randomly assigned to either the SpSi group (n = 60) or placebo group (n = 60). Over 6 months, the participants received either 3.5 g of specific 1% silicon-enriched spirulina (SpSi group) or placebo tablets daily. The primary outcome was the assessment of arterial wall pressure waveforms, which included blood pressure (BP) readings and the determination of the aortic pulse wave velocity (aPWV). Secondary outcomes included the vasomotor endothelial function through post-ischemic vasorelaxation, measured using the reactive hyperemia index (RHI), and carotid intima-media thickness. Results: When considering the entire sample, none of the studied parameters differed between the placebo and SpSi groups. However, when focusing on individuals with high-normal blood pressure (i.e., systolic BP between 130 and 150 mmHg) and aPWV levels above cutoff values (>10 m/s), the BP decreased by 8% (p < 0.001) and aPWV decreased by 13.5% (p < 0.0001) in subjects receiving SpSi. In individuals with BP and aPWV levels below the cutoff values, no effect was observed. Conclusions: In healthy elderly individuals, SpSi supplementation improved high-normal blood pressure and aortic pulse wave velocity, suggesting an enhanced vascular function.

Silicon in prevention of atherosclerosis and other age-related diseases

Researchers' interest in silicon as an element important for the functioning of the animal and human body began in the 1970s. Soluble compounds of silicon bioavailable from water and food seem to have important meaning for life processes occurring in the body. So far, researchers have focused on the significance of silicon for the development of bones and connective tissue, and its role in preventing neurodegenerative diseases and atherosclerosis. Despite numerous studies, the role of silicon as an active element in the human body is poorly understood. Since the involvement of lipid oxidation and inflammatory processes in the pathogenesis of atherosclerosis is well known, this article summarizes and discusses the current research and scientific observations regarding silicon, primarily in terms of its beneficial influence on redox and anti-inflammatory reactions and the lipid profile. The association of silicon with the stabilization of the structure of glycosaminoglycans and their protein complexes may also support the anti-atherosclerotic effect. The authors attempted to collect and present existing publications that could confirm the beneficial role of dietary silicon in the prevention of age-related diseases and explain the potential mechanisms of its action.

Marine Natural Products: A Potential Source of Anti-hepatocellular Carcinoma Drugs

Hepatocellular carcinoma (HCC) has high associated morbidity and mortality rates. Although chemical medication represents a primary HCC treatment strategy, low response rates and therapeutic resistance serve to reduce its efficacy. Hence, identifying novel effective drugs is urgently needed, and many researchers have sought to identify new anti-cancer drugs from marine organisms. The marine population is considered a "blue drug bank" of unique anti-cancer compounds with diverse groups of chemical structures. Here, we discuss marine-derived compounds, including PM060184 and bryostatin-1, with demonstrated anti-cancer activity in vitro or in vivo. Based on the marine source (sponges, algae, coral, bacteria, and fungi), we introduce pharmacological parameters, compound-induced cytotoxicity, effects on apoptosis and metastasis, and potential molecular mechanisms. Cumulatively, this review provides insights into anti-HCC research conducted to date in the field of marine natural products and marine-derived compounds, as well as the potential pharmacological mechanisms of these compounds and their status in drug development.

Application of either nano fibrillated cellulose methotrexate or nano silicon dioxide methotrexate composites against renal fibrosis in leukemia rat model

Cellulose derivatives have got growing interest due to their relative abundance and ability to sustain the release of medicaments. In this study, micro- and nano-fibrillated cellulose were prepared from rice straw and used as drug carriers. Both carriers in addition to another one which is nano silicon dioxide were characterized with various techniques. Methotrexate was chosen to be loaded on nano-fibrillated cellulose and nano silicon dioxide. Both methotrexate carriers were evaluated for their possible protective role against renal fibrosis induced by methotrexate in leukemia rat model. Results of this study exhibited that loading methotrexate on either nano-fibrillated cellulose or nano silicon dioxide seems to have an ameliorative role on renal function tests, inflammatory and fibrotic markers of renal tissues. Moreover, the sustained release of methotrexate for long time period maintained by nano-fibrillated cellulose carrier gives it more priority than nano silicon dioxide to be used as an effective novel drug carrier in further medical applications with minimal side effects on kidney tissue in leukemia model.

Dietary Supplementation with Silicon-Enriched Spirulina Improves Arterial Remodeling and Function in Hypertensive Rats

Vascular aging is characterized by increase in arterial stiffness and remodeling of the arterial wall with a loss of elastic properties. Silicon is an essential trace element highly present in arteries. It is involved in the constitution and stabilization of elastin fibers. The nutritional supply and bioavailability of silicon are often inadequate. Spirulina (Sp), micro algae have recognized nutritional properties and are able to incorporate minerals in a bioavailable form. We evaluated the effects of nutritional supplementation with silicon-enriched spirulina (SpSi) on arterial system structure and function in hypertension. Experiments were performed on hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats supplemented with SpSi or Sp over a period of three months. Arterial pressure, vascular function and morphometric parameters of thoracic aorta were analyzed. SpSi supplementation lowered arterial pressure in SHR and minimized morphometric alterations induced by hypertension. Aortic wall thickness and elastic fibers fragmentation were partially reversed. Collagen and elastin levels were increased in association with extracellular matrix degradation decrease. Vascular reactivity was improved with better contractile and vasorelaxant responses to various agonists. No changes were observed in SHR supplemented with Sp. The beneficial effects of SpSi supplementation evidenced here, may be attributable to Si enrichment and offer interesting opportunities to prevent cardiovascular risks.

Effect of spirulina and silicon-enriched spirulina on metabolic syndrome features, oxidative stress and mitochondrial activity in Zucker fatty rats

The use of Spirulina platensis (Sp) as a functional food was suggested decades ago. Biological incorporation of Silicon (Si) into Sp increases its bioavailability for potential food supplement applications. This work aimed at determining the effects of Sp and Si-enriched Sp (Sp+Si) on metabolic syndrome features in Zucker fatty rats. Thirty Zucker fatty rats were divided into three groups and supplemented with placebo or Sp or Sp+Si croquettes for 12 weeks. Food consumption, glucose intolerance, hepatic steatosis, and mitochondrial and oxidative stress were determined. Zucker fatty rats exhibited several hepatic metabolic alterations as well as mitochondrial and oxidative stress perturbations. The intake of Sp increased plasma TG levels and decreased the hepatic NADPH oxidase activity and ameliorated transitorily the glucose intolerance. However, Si-spirulina does not appear to have more beneficial effects than spirulina alone. Other experiments with different species of rats/mice, different diets, or durations of diet intake should be undertaken to confirm or infirm these results. PRACTICAL APPLICATIONS: Glucose intolerance and hepatic steatosis, two major components of metabolic syndrome, are increasing and becomes a major public health issue. Use of Spirulina platensis (Sp) as a functional food was suggested as a protein-dense food source. Bioavailable silicon (Si) may be an essential nutrient for higher animals, including humans. Sp but not Sp+Si decreased liver NADPH oxidase activity and improved transitorily glucose tolerance. This is the first study where Sp and Sp+Si effect on glucose intolerance is reported in Zucker rat. Other experiments should be undertaken to confirm or infirm invalidate the beneficial effects of Sp+Si supplement in the metabolic syndrome features.

Spirulina platensis and silicon-enriched spirulina equally improve glucose tolerance and decrease the enzymatic activity of hepatic NADPH oxidase in obesogenic diet-fed rats

The prevalence of metabolic syndrome components, such as obesity, glucose intolerance and hepatic steatosis, is rapidly increasing and becoming a major issue of public health. The present work was designed to determine the effects of Spirulina platensis (Sp) algae and silicon-enriched Sp on major metabolic syndrome components in obesogenic diet-fed rats. Forty male Wistar rats were divided into 4 groups. Ten rats were fed a control diet and 30 rats were fed a high fat (HF) diet. The HF groups were divided into three groups and supplemented with placebo or Sp or Si-enriched Sp for 12 weeks. Dietary intake and body weight were recorded. Oral glucose tolerance test and surrogate metabolic syndrome (insulin, leptin, adiponectin and lipids), mitochondrial function (enzymatic activity of respiratory chain complexes and β-hydroxyacyl-CoA dehydrogenase), NADPH oxidase activity and several long-established oxidative stress markers were measured in the blood and liver. The HF diet induced obesity, glucose intolerance, hepatic steatosis and huge metabolic alterations, associated with higher NADPH oxidase activity and lower hepatic sulfhydryl group and glutathione contents. Otherwise, the Sp and Sp + Si supplements showed some interesting effects on rat characteristics and particularly on blood and hepatic metabolic parameters. Indeed, the intake of Sp or Sp + Si mainly improved glucose tolerance and decreased the enzymatic activity of hepatic NADPH oxidase. Overall, Si supplementation of spirulina does not appear to have more beneficial effects than spirulina alone. Other experiments with different species of rats/mice, different diets or different durations of diet intake should be undertaken to confirm or invalidate these results.

Arterial Stiffness and Trace Elements in Apparently Healthy Population- A Cross-sectional Study

INTRODUCTION

Stiffening of arteries is a natural ageing process. Any diseases/disorders or risk factors that escalate oxidative stress, microvascular inflammation and endothelial damage may promote to premature vascular stiffening. Any imbalance in these trace element levels may independently contribute to the changes in the components in the arterial wall and thus, arterial stiffness via one or more mechanisms.

AIM

To evaluate the severity of arterial stiffness in apparently healthy population and also to evaluate role of various risk factors and trace elements in the severity of arterial stiffness.

MATERIALS AND METHODS

Male and female subjects living in urban and rural areas of Nellore district, Andhra Pradesh, India, between 20-60 years, apparently normal as judged by the clinician basing on clinical and laboratory findings, were studied. Carotid-Femoral Pulse Wave Velocity (cf-PWV) a marker of arterial stiffness was assessed using non-invasive blood pressure curve monitoring (periscope). Furthermore, we also estimated serum levels of Copper (Cu), Zinc (Zn), Selenium (Se), chromium (Cr), Aluminium (Al), silicon (Si), Manganese (Mn), Molybdenum (Mb), Vanadium (Vn) and lead (Pb) using atomic absorption spectrophotometer. ANOVA and Chi-Square test were used to study the clinical correlations between severity of arterial stiffness, risk factors and trace elements.

RESULTS

A total of 737 apparently healthy subjects participated in this cross-sectional study. Of the total 542 (73.5%) were from rural and the remaining 195 (26.5%) were living in urban areas, 328 (44.5%) were males, and 409 (55.5%) were females. A 63.5% (468/737) had normal arterial stiffness followed by 14.5% (107/737) with mild stiffness, 7% (57/737) had moderate stiffness and 14.2% (105/737) had severe arterial stiffness. Smoking, alcohol, blood pressures, fasting blood sugar, and total cholesterol, Cu, Al and Vn correlated (p<0.05) with different grades of arterial stiffness.

CONCLUSION

A 36.5% had high arterial stiffness despite being apparently healthy. Smoking, alcohol, blood pressures, fasting blood sugars, and total cholesterol, Cu, Al and Vn could have contributed for such an abnormality. Caution has to be executed while understanding the study results since the pathophysiological process is complex.

Silicon as neuroprotector or neurotoxic in the human neuroblastoma SH-SY5Y cell line

Silicon (Si) is a trace element that has been considered to be an environmental contaminant for many years, although different studies have recently reported it is an essential element for living cells. The present study tested the ability of different concentrations of Si G57™ to induce neuroprotection or neurotoxicity over 24 h in the SH-SY5Y human neuroblastoma cell line. Cell viability, cellular proliferation, LDH release, ROS, antioxidant capacity, TBARS, caspase-3, -8 and -9, DNA fragmentation, and TNF-α levels were evaluated. Low Si doses (50-250 ng mL(-1)) increased the cell viability and reduced caspase-3 and -8 activities and TNF-α level. The increase in cell viability was independent of any proliferative effect as there was no variation in cyclin E and PCNA levels. At higher concentrations, Si increased caspase-3, as well as TBARS, LDH, DNA fragmentation, and TNF-α releases. Altogether, these results suggest that Si could act either as a neuroprotector or a neurotoxic agent depending on the concentration tested. This study emphasizes the importance of developing new neuroprotective therapies based on low Si doses.

Dietary Silicon Deficiency Does Not Exacerbate Diet-Induced Fatty Lesions in Female ApoE Knockout Mice

BACKGROUND

Dietary silicon has been positively linked with vascular health and protection against atherosclerotic plaque formation, but the mechanism of action is unclear.

OBJECTIVES

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.

METHODS

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).

RESULTS

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.

CONCLUSIONS

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.

Dietary silicon-enriched spirulina improves early atherosclerosis markers in hamsters on a high-fat diet

OBJECTIVE

The aim of this study was to investigate the effects of dietary silicon-enriched spirulina (SES) on atherosclerosis.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Corals and their potential applications to integrative medicine

Over the last few years, we have pursued the use and exploitation of invertebrate immune systems, most notably their humoral products, to determine what effects their complex molecules might exert on humans, specifically their potential for therapeutic applications. This endeavor, called “bioprospecting,” is an emerging necessity for biomedical research. In order to treat the currently “untreatable,” or to discover more efficient treatment modalities, all options and potential sources must be exhausted so that we can provide the best care to patients, that is, proceed from forest and ocean ecosystems through the laboratory to the bedside. Here, we review current research findings that have yielded therapeutic benefits, particularly as derived from soft and hard corals. Several applications have already been demonstrated, including anti-inflammatory properties, anticancer properties, bone repair, and neurological benefits.

Silicic acid in drinking water prevents age-related alterations in the endothelium-dependent vascular relaxation modulating eNOS and AQP1 expression in experimental mice: an immunohistochemical study

The maintenance of endothelial integrity is of great importance in coping with age-related vascular alterations. Endothelium-derived nitric oxide is one of the various vasoactive substances able to regulate vascular tone and homeostasis, and whose decrease is known to be related with senescence in endothelial cells. There are reports on the efficacy of silicon, especially as silicic acid, in protecting vascular integrity during age-related vascular diseases. The aim of this study was to evaluate the ability of supplementation of silicic acid in drinking water in the maintenance of vascular health in a mouse model of early physiological aging. In particular, we evaluated the relationship between Si supplementation and endothelial nitric oxide synthase (eNOS) expression, taking into account also the aquaporin-1 (AQP-1) isoform that, as recently reported, seems to be involved in nitric oxide transport across cell membranes. Our results showed that silicic acid supplementation increased both eNOS and AQP-1 expression, suggesting that silicic acid modulation of endothelial nitric oxide synthase and aquaporin-1 could represent a potential strategy against age-related vascular senescence.

Biological and therapeutic effects of ortho-silicic acid and some ortho-silicic acid-releasing compounds: New perspectives for therapy

Silicon (Si) is the most abundant element present in the Earth's crust besides oxygen. However, the exact biological roles of silicon remain unknown. Moreover, the ortho-silicic acid (H4SiO4), as a major form of bioavailable silicon for both humans and animals, has not been given adequate attention so far. Silicon has already been associated with bone mineralization, collagen synthesis, skin, hair and nails health atherosclerosis, Alzheimer disease, immune system enhancement, and with some other disorders or pharmacological effects. Beside the ortho-silicic acid and its stabilized formulations such as choline chloride-stabilized ortho-silicic acid and sodium or potassium silicates (e.g. M2SiO3; M= Na,K), the most important sources that release ortho-silicic acid as a bioavailable form of silicon are: colloidal silicic acid (hydrated silica gel), silica gel (amorphous silicon dioxide), and zeolites. Although all these compounds are characterized by substantial water insolubility, they release small, but significant, equilibrium concentration of ortho-silicic acid (H4SiO4) in contact with water and physiological fluids. Even though certain pharmacological effects of these compounds might be attributed to specific structural characteristics that result in profound adsorption and absorption properties, they all exhibit similar pharmacological profiles readily comparable to ortho-silicic acid effects. The most unusual ortho-silicic acid-releasing agents are certain types of zeolites, a class of aluminosilicates with well described ion(cation)-exchange properties. Numerous biological activities of some types of zeolites documented so far might probably be attributable to the ortho-silicic acid-releasing property. In this review, we therefore discuss biological and potential therapeutic effects of ortho-silicic acid and ortho-silicic acid -releasing silicon compounds as its major natural sources.

Silicon: the health benefits of a metalloid

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.