Mangiferin positively regulates osteoblast differentiation and suppresses osteoclast differentiation.

Mangiferin is a polyphenolic compound present in Salacia reticulata. It has been reported to reduce bone destruction and inhibit osteoclastic differentiation. This study aimed to determine whether mangiferin directly affects osteoblast and osteoclast proliferation and differentiation, and gene expression in MC3T3­E1 osteoblastic cells and osteoclast­like cells derived from primary mouse bone marrow macrophage cells. Mangiferin induced significantly greater WST­1 activity, indicating increased cell proliferation. Mangiferin induced significantly increased alkaline phosphatase staining, indicating greater cell differentiation. Reverse transcription­polymerase chain reaction (RT­PCR) demonstrated that mangiferin significantly increased the mRNA level of runt­related transcription factor 2 (RunX2), but did not affect RunX1 mRNA expression. Mangiferin significantly reduced the formation of tartrate­resistant acid phosphatase­positive multinuclear cells. RT­PCR demonstrated that mangiferin significantly increased the mRNA level of estrogen receptor ß (ERß), but did not affect the expression of other osteoclast­associated genes. Mangiferin may inhibit osteoclastic bone resorption by suppressing differentiation of osteoclasts and promoting expression of ERß mRNA in mouse bone marrow macrophage cells. It also has potential to promote osteoblastic bone formation by promoting cell proliferation and inducing cell differentiation in preosteoblast MC3T3­E1 cells via RunX2. Mangiferin may therefore be useful in improving bone disease outcomes.

Oral collagen-derived dipeptides, prolyl-hydroxyproline and hydroxyprolyl-glycine, ameliorate skin barrier dysfunction and alter gene expression profiles in the skin.

Oral supplementation with collagen hydrolysate (CH) has been shown to improve the condition of the skin in humans and experimental animals. Several hydroxyproline-containing oligo-peptides were previously detected in human peripheral blood after the ingestion of CH, and the two dipeptides, prolyl-hydroxyproline (PO) and hydroxyprolyl-glycine (OG), have been proposed to have beneficial effects on human health. When HR-1 hairless mice were fed a HR-AD diet, which lacked magnesium and zinc, transepidermal water loss (TEWL) increased and water content of stratum corneum decreased. In the present study, we investigated the effects of dietary PO and OG on skin barrier dysfunction in HR-1 hairless mice. Mice were fed a HR-AD diet with or without PO (0.15%) and OG (0.15%) for 35 consecutive days. The administration of PO and OG significantly decreased TEWL, and significantly increased water content of stratum corneum. A DNA microarray analysis of the dorsal skin revealed differences in gene expression between the group administered PO and OG and the control group. We also identified muscle-related Gene Ontology as a result of analyzing the up-regulated genes. These results suggested that the administration of PO and OG improved skin barrier dysfunction and altered muscle-related gene expression.

Collagen-derived dipeptide prolyl-hydroxyproline promotes differentiation of MC3T3-E1 osteoblastic cells.

Prolyl-hydroxyproline (Pro-Hyp) is one of the major constituents of collagen-derived dipeptides. The objective of this study was to investigate the effects of Pro-Hyp on the proliferation and differentiation of MC3T3-E1 osteoblastic cells. Addition of Pro-Hyp did not affect MC3T3-E1 cell proliferation and matrix mineralization but alkaline phosphatase activity was significantly increased. Furthermore, cells treated with Pro-Hyp significantly upregulated gene expression of Runx2, Osterix, and Col1α1. These results indicate that Pro-Hyp promotes osteoblast differentiation. This study demonstrates for the first time that Pro-Hyp has a positive effect on osteoblast differentiation with upregulation of Runx2, Osterix, and Collα1 gene expression.

Acute enhancement of non-rapid eye movement sleep in rats after drinking water contaminated with cadmium chloride.

Cadmium (Cd) is a heavy metal widely used or effused by industries. Serious environmental Cd pollution has been reported over the past two centuries, whereas the mechanisms underlying Cd-mediated diseases are not fully understood. Interestingly, an increase in reactive oxygen species (ROS) after Cd exposure has been shown. Our group has demonstrated that sleep is triggered via accumulation of ROS during neuronal activities, and we thus hypothesize the involvement of Cd poisoning in sleep-wake irregularities. In the present study, we analyzed the effects of Cd intake (1-100 ppm CdCl2 in drinking water) on rats by monitoring sleep encephalograms and locomotor activities. The results demonstrated that 100 ppm CdCl2 administration for 28 h was sufficient to increase non-rapid-eye-movement (non-REM) sleep and reduce locomotor activities during the night (the rat active phase). In contrast, free-running locomotor rhythms under constant dim red light and their re-entrainment to 12:12-h light/dark cycles were intact under chronic (1 month) 100 ppm CdCl2 administrations, suggesting a limited influence on circadian clock movements at this dosage. The relative amount of oxidized glutathione increased in the brain after the 28-h 100 ppm CdCl2 administrations similar to the levels in cultured astrocytes receiving H2O2 or CdCl2 in culture medium. Therefore, we propose Cd-induced sleep as a consequence of oxidative stress. As oxidized glutathione is an endogenous sleep substance, we suggest that Cd rapidly induces sleepiness and influences activity performance by occupying intrinsic sleep-inducing mechanisms. In conclusion, we propose increased non-REM sleep during the active phase as an index of acute Cd exposure.

Computational simulation of hypertrophic cardiomyopathy mutations in troponin I: influence of increased myofilament calcium sensitivity on isometric force, ATPase and [Ca2+]i.

Familial hypertrophic cardiomyopathy (FHC) is an inherited disease that is characterized by ventricular hypertrophy, cardiac arrhythmias and increased risk of premature sudden death. FHC is caused by autosomal-dominant mutations in genes for a number of sarcomeric proteins; many mutations in Ca(2+)-regulatory proteins of the cardiac thin filament are associated with increased Ca(2+) sensitivity of myofilament function. Computational simulations were used to investigate the possibility that these mutations could affect the Ca(2+) transient and mechanical response of a myocyte during a single cardiac cycle. We used existing experimental data for specific mutations of cardiac troponin I that exhibit increased Ca(2+) sensitivity in physiological and biophysical assays. The simulated Ca(2+) transients were used as input for a three-dimensional half-sarcomere biomechanical model with filament compliance to predict the resulting force. Mutations with the highest Ca(2+) affinity (lowest K(m)) values, exhibit the largest decrease in peak Ca(2+) assuming a constant influx of Ca(2+) into the cytoplasm; they also prolong Ca(2+) removal but have little effect on diastolic Ca(2+). Biomechanical model results suggest that these cTnI mutants would increase peak force despite the decrease in peak [Ca(2+)](i). There is a corresponding increase in net ATP hydrolysis, with no change in tension cost (ATP hydrolyzed per unit of time-integrated tension). These simulations suggest that myofilament-initiated hypertrophic signaling could be associated with decreased [Ca(2+)](i), increased stress/strain, and/or increased ATP flux.

Effects of rapamycin on cardiac and skeletal muscle contraction and crossbridge cycling.

The immunosuppressant drug rapamycin attenuates the effects of many cardiac hypertrophy stimuli both in vitro and in vivo. Although rapamycin's inhibition of mammalian target of rapamycin and its associated signaling pathways is well established, it is likely that other signaling pathways are more important for some forms of cardiac hypertrophy. Considering the central role of myofilament protein mutations in familial hypertrophic cardiomyopathies, we tested the hypothesis that rapamycin's antihypertrophy action in the heart is due to direct effects of the drug on myofilament protein function. We found little or no effect of rapamycin (10(-8)-10(-4) M) on maximum Ca(2+)-activated isometric force, whereas Ca(2+) sensitivity was increased at some rapamycin concentrations in rabbit skeletal and cardiac and rat cardiac muscle. At concentrations that increased Ca(2+) sensitivity of isometric force, rapamycin reversibly inhibited kinetics of isometric tension redevelopment (k(TR)) in rabbit skeletal, but not cardiac, muscle. The greatest inhibition (approximately 50%) was at intermediate levels of Ca(2+) activation, with less inhibition of k(TR) (approximately 15%) at maximum Ca(2+) activation levels. Rapamycin (10(-7) M) increased actin filament sliding speed (approximately 11%) in motility assays but inhibited sliding at 10(-5) to 10(-4) M. These results indicate that rapamycin has a greater effect on Ca(2+) regulatory proteins of the thin filament than on actomyosin interactions. These effects, however, are not consistent with rapamycin's antihypertrophic activity being mediated through direct effects on myofilament contractility.