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Genistein and daidzein are known to have both beneficial and adverse effects on human health due to their many biological actions at the cellular level. Both isoflavones have been shown to inhibit GLUT-mediated glucose transport across the plasma membrane of mammalian cells. Since lysosomal membrane transport is essential for maintaining cellular homeostasis, the present study examined the effects of genistein and daidzein on glucose and sulphate transport in isolated rat liver lysosomes. Both genistein and daidzein significantly inhibited lysosomal glucose uptake. Genistein was a more potent glucose transport inhibitor than daidzein, with a half-maximum inhibitory concentration (IC50) of 45 μmol/l compared with 71 μmol/l for daidzein. Uptake kinetics of d-glucose showed a significant decrease in Vmax (control:genistein treat = 1489 (sem 91):507 (sem 76) pmol/unit of β-hexosaminidase per 15 s) without a change in Km. The presence of 50 μm-genistein in the medium also reduced glucose efflux from lysosomes preloaded with 100 mm-d-glucose. Genistein also inhibited lysosomal sulphate transport. Similar to its effects on glucose uptake kinetics, genistein treatment caused a significant decrease in sulphate uptake Vmax (control:genistein treat = 87 (sem 4):59 (sem 5) pmol/unit of β-hexosaminidase per 30 s), while the Km was not affected. The evidence provided by the present study suggests that the most likely mechanism of lysosomal glucose transport inhibition by genistein is via direct interaction between genistein and the transporter, rather than mediation by tyrosine kinase inactivation. Genistein likely has a similar mechanism of directly inhibiting sulphate transporter.
In this study, the mechanical properties of human dental structures have been investigated by using instrumented nanoindentation. Immersion in solutions containing Streptococcus mutans, which is the principal cause of dental caries, was applied to tooth specimens to clarify its effect on the microstructure and mechanical properties of the dental structures. With an extended time of up to 16 h, the pH value of the S. mutans solutions dropped from 7.3 to 5.8. Therefore, after immersion in the S. mutans solutions for 16 h, slight erosions of the dental structures began; after 64 h, severe tooth decay occurred with obviously etched dental features. After 128 h, the elastic modulus of enamel and dentine dropped to 85 and 67%, respectively, of the original values of untreated specimens, and the hardness dropped to 88 and 55%, respectively.
The present study was designed to examine the effects of habitual consumption of Taiwanese vegetarian diets on hormonal secretion, and on lipid and glycaemic control. Of the ninety-eight healthy female adults recruited from Hualien, Taiwan (aged 31–45 years), forty-nine were Buddhist lactovegetarians and forty-nine were omnivores. Dietary intakes were measured, and blood levels of nutrients and hormones were analysed. Vegetarians consumed less energy, fat and protein, but more fibre than the omnivores. Compared with the omnivores, the vegetarians had, on average, lower BMI and smaller waist circumference. Except for slightly lower levels of thyroxine (T4) in vegetarians, vegetarians and omnivores both showed similar levels of triiodothyronine (T3), free T4, thyroid-stimulating hormone, T3:T4 ratio and cortisol. Compared with the omnivores, the vegetarians had significantly lower levels of fasting insulin (median: 35·3 v. 50·6pmol/l) and plasma glucose (mean: 4·7 (se 0·05) v. 4·9 (se 0·05) mmol/l). Insulin resistance, as calculated by the homeostasis model assessment method, was significantly lower in the vegetarians than in the omnivores (median: 1·10 v. 1·56), while β-cell function was not different between the two groups. BMI and diet were both independent predictors for insulin resistance, and contributed 18 and 15% of the variation in insulin resistance, respectively. In conclusion, Taiwanese vegetarians had lower glucose and insulin levels and higher insulin sensitivity than did the omnivores. Diet and lower BMI were partially responsible for the high insulin sensitivity observed in young Taiwanese vegetarians.
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