Mee-Young Shin

Diosgenin stimulates osteogenic activity by increasing bone matrix protein synthesis and bone-specific transcription factor Runx2 in osteoblastic MC3T3-E1 cells☆

Diosgenin, a steroid saponin extracted from the root of wild yam (Dioscorea villossa) is claimed to have osteogenic property. However, detailed studies providing evidence to this claim have not been fully undertaken. In this study, we investigated the effect of diosgenin on the osteogenesis of murine MC3T3-E1 osteoblastic cells. Cells were cultured with varying levels of diosgenin (0-10 μM) within 25 days of bone formation period. Diosgenin was found to stimulate proliferation within the range of 0.01-5 μM using MTT assay. The medium and cellular levels of Type 1 collagen and alkaline phosphatase (ALP), both of which are major bone matrix proteins, increased within the low range of diosgenin concentration (>0-3 μM), and this pattern was further confirmed by collagen and ALP staining of the extracellular matrix (ECM). The cellular protein expression of ALP and collagen Type 1 was also increased at 0.1-1 μM diosgenin treatment as analyzed by Western blot. Calcium deposition within the ECM also showed the same pattern as assessed by Alizarin Red S and Von Kossa staining. Bone-specific transcription factor runt-related transcription factor 2 (Runx2) and Runx2-regulated osteopontin protein expressions were induced at low concentration (0.1-1 μM) and again decreased with high diosgenin concentrations. Based on our findings, our study suggests that diosgenin can enhance bone formation by stimulating the synthesis and secretion of Type 1 collagen and ALP and bone marker proteins Runx2 and osteopontin expression. The increased levels of these marker proteins, in turn, can increase the formation of calcium deposits within the ECM thereby increasing bone formation.

Yam (Dioscorea batatas) Root and Bark Extracts Stimulate Osteoblast Mineralization by Increasing Ca and P Accumulation and Alkaline Phosphatase Activity.

Yam (Dioscorea batatas) is widely consumed as functional food for health promotion mainly in East Asia countries. We assessed whether yam root (tuber) or bark (peel) extracts stimulated the activity of osteoblasts for osteogenesis. MC3T3-E1 cells (mouse osteoblasts) were treated with yam root extracts (water or methanol) (study I) or bark extracts (water or hexane) (study II) within 0~10 μg/mL during the periods of osteoblast proliferation (5~10 day), matrix maturation (11~15 day) and mineralization (16~20 day) as appropriate. In study I, both yam root water and methanol extracts increased cell proliferation as concentration-dependent manner. Cellular collagen synthesis and alkaline phosphatase (ALP) activity, both the indicators of bone matrix protein and inorganic phosphate production for calcification respectively, were also increased by yam root water and methanol extract. Osteoblast calcification as cell matrix Ca and P accumulation was also increased by the addition of yam root extracts. In study II, yam bark extracts (water and hexane) increased osteoblast proliferation and differentiation, as collagen synthesis and ALP activity and osteoblast matrix Ca and P deposition. The study results suggested that both yam root and bark extracts stimulate osteogenic function in osteoblasts by stimulating bone matrix maturation by increasing collagen synthesis, ALP activity, and matrix mineralization.

Zinc Restored the Decreased Vascular Smooth Muscle Cell Viability under Atherosclerotic Calcification Conditions

Zinc is considered to be involved in maintaining healthy vascular condition. Atherosclerotic calcification of vascular smooth muscle cells (VSMCs) occurs via the mechanism of cell death; therefore, cell viability is a critical factor for preventing VSMC calcification. In this study, we tested whether zinc affected VSMC viability under both normal physiological non-calcifying (0 mM P) and atherosclerotic calcifying conditions (3 and 5 mM P), since VSMC physiological characters change during the VSMC calcification process. The study results showed that an optimal zinc level (15 μM) restored the decreased VSMC viability which was induced under low zinc levels (0 and 1 μM) and calcifying conditions (3 and 5 mM P) at 9 and 15 days culture. This zinc-protecting effect for VSMC viability is more prominent under atherosclerotic calcifying condition (3 and 5 mM P) than normal condition (0 mM P). Also, the increased VSMC viability was consistent with the decreased Ca and P accumulation in VSMC cell layers. The results suggested that zinc could be an effective biomineral for preventing VSMC calcification under atherosclerotic calcifying conditions.

Phosphate-Induced Rat Vascular Smooth Muscle Cell Calcification and the Implication of Zinc Deficiency in A7r5 Cell Viability

The calcification of vascular smooth muscle cells (VSMCs) is considered one of the major contributors for vascular disease. Phosphate is known as the inducer for VSMC calcification. In this study, we assessed whether phosphate affected cell viability and fetuin-A, a calcification inhibitor protein, both which are related to VSMC calcification. Also, VSMC viability by zinc level was assessed. The results showed that phosphate increased Ca and P deposition in VSMCs (A7r5 cell line, rat aorta origin). This phosphate-induced Ca and P deposition was consistent with the decreased A7r5 cell viability (P<0.05), which implies phosphate-induced calcification in A7r5 cells might be due to the decreased VSMC cell viability. As phosphate increased, the protein expression of fetuin-A protein was up-regulated. A7r5 cell viability decreased as the addition of cellular zinc level was decreased (P<0.05). The results suggested that zinc deficiency causes the decreased cell viability and it would be the future study to clarify how zinc does act for VSMC cell viability. The results suggest that the decreased VSMC viability by high P or low Zn in VSMCs may be the risk factor for vascular disease.

The Contents of Heavy Metals (Cd, Cr, As, Pb, Ni, and Sn) in the Selected Commercial Yam Powder Products in South Korea

Yam (Dioscorea) has long been used as foods and folk medicine with the approved positive effects for health promotion. Although consumption of yam products is increasing for health promotion, reports for the metal contamination in commercial yam powder products to protect the consumers are lacking. In this study, we aimed to assess whether the commercial yam powder products were heavy metal contaminated or not using the yam products from six commercial products from various places in South Korea. The contents of heavy metals (Cd, Cr, As, Pb, Ni, and Sn) in yam powder products were measured and compared to national and international food standard levels. Also, the metal contamination was monitored during the food manufacturing steps. The study results showed that the contents of heavy metals (Cd, Cr, As, and Pb) in yam powder products are similar to those in national ‘roots and tubers’ as well as in various crops. In comparison to three international standard levels (EU, Codex and Korea), Cd content in yam powder products was lower but Pb content was 5 times higher. Also, Pb, Ni, and Sn may have the potential to be contaminated during food manufacturing steps. In conclusion, the level of heavy metals (Cd, Cr, As, Ni, and Sn) except Pb is considered relatively safe on comparison to national and international food standard levels.

The Supplementation of Yam Powder Products Can Give the Nutritional Benefits of the Antioxidant Mineral (Cu, Zn, Mn, Fe and Se) Intakes

Yam has been recognized having the beneficial effects for the prevention of various diseases, such as cancer, immunity, infection and obesity etc. There is increasing consideration to supplement the antioxidant nutrients to make up the lack of the antioxidant nutrient intakes. No study has been reported for the analysis of antioxidant mineral contents and comparison to dietary recommended intake for the sense of health promotion. In our study, we analyzed the contents of antioxidant trace elements (Zn, Mn, Fe, Cu and Se) and Cr contents in cultivated Korean yam powders for evaluation of nutrient intake aspects. We collected the commercial yam powders from six different cultivated areas in the South Korea and measured antioxidant minerals (Zn, Mn, Fe, Cu and Se) and Cr contents using trace element-free plasma spectrometer (ICP) or atomic absorption spectrometer (AAS) after dry-ashing and then wet-acid digestion. The accuracy of mineral analysis method was confirmed by the mineral analysis of standard reference material. Each analyzed element contents in yam were compared to dietary reference intakes of Koreans (KDRIs). The average levels of trace elements (Zn, Mn, Fe, Cu, Se and Cr) in yam powders were 18.3, 11.9, 36.0, 3.7, 1.9 and 1.27 μg/g yam powder, respectively. The intakes of Zn, Fe, Cu and Se of which KDRIs is determined, are accounted as being up to 23.8%, 55.6%, 32.5% and 236% recommended intake (RI) of KDRIs, if daily yam supplementation (50 g) of commercial instruction would be considered. The intake of Mn is about 25% adequate intake (AI) of KDRIs with the daily supplementation of yam powder. Most of mineral intakes from daily yam supplementation were with the range of non-detectable to <10% upper limit (UL) level, which is very much safe. The study results show that daily supplementation of Korean yam power is beneficial to provide the supplemental nutrient intake and also is safe, if the suggested dosage would be considered.