Prevention of Disuse Muscle Atrophy by Dietary Ingestion of 8-Prenylnaringenin in Denervated Mice

Flavonoids have attracted considerable attention in relation to their effects upon health. 8-Prenylnaringenin (8-PN) is found in the common hop (Humulus lupulus) and assumed to be responsible for the health impact of beer consumption. We wanted to clarify the effects of prenylation on the physiological functions of dietary flavonoids by comparing the effects of 8-PN with that of intact naringenin in the prevention of disuse muscle atrophy using a model of denervation in mice. Consumption of 8-PN (but not naringenin) prevented loss of weight in the gastrocnemius muscle further supported by the lack of induction of the protein content of a key ubiquitin ligase involved in muscle atrophy, atrogin-1, and by the activation of Akt phosphorylation. 8-PN content in the gastrocnemius muscle was tenfold higher than that of naringenin. These results suggested that, compared with naringenin, 8-PN was effectively concentrated into skeletal muscle to exert its preventive effects upon disuse muscle atrophy. It is likely that prenylation generates novel functions for 8-PN by enhancing its accumulation into muscle tissue through dietary intake

Maackiain Suppresses H1R and IL-4 Gene Transcriptions

Kujin contains antiallergic compounds that inhibit upregulation of histamine H1 receptor (H1R) and interleukin (IL)‐4 gene expression. However, the underlying mechanism remains unknown. We sought to identify a Kujin‐derived antiallergic compound and investigate its mechanism of action. The H1R and IL‐4 mRNA levels were determined by real‐time quantitative RT‐PCR. To investigate the effects of maackiain in vivo, toluene‐2,4‐diisocyanate (TDI)‐sensitized rats were used as a nasal hypersensitivity animal model. We identified (−)‐maackiain as the responsible component. Synthetic maackiain showed stereoselectivity for the suppression of IL‐4 gene expression but not for H1R gene expression, suggesting distinct target proteins for transcriptional signaling. (−)‐Maackiain inhibited of PKCδ translocation to the Golgi and phosphorylation of Tyr311 on PKCδ, which led to the suppression of H1R gene transcription. However, (−)‐maackiain did not show any antioxidant activity or inhibition of PKCδ enzymatic activity per se. Pretreatment with maackiain alleviated nasal symptoms and suppressed TDI‐induced upregulations of H1R and IL‐4 gene expressions in TDI‐sensitized rats. These data suggest that (−)‐maackiain is a novel antiallergic compound that alleviates nasal symptoms in TDI‐sensitized allergy model rats through the inhibition of H1R and IL‐4 gene expression. The molecular mechanism underlying its suppressive effect for H1R gene expression is mediated by the inhibition of PKCδ activation

Comparative Gene Analysis Focused on Silica Cell Wall Formation: Identification of Diatom-Specific SET Domain Protein Methyltransferases

Silica cell walls of diatoms have attracted attention as a source of nanostructured functional materials and have immense potential for a variety of applications. Previous studies of silica cell wall formation have identified numerous involved proteins, but most of these proteins are species-specific and are not conserved among diatoms. However, because the basic process of diatom cell wall formation is common to all diatom species, ubiquitous proteins and molecules will reveal the mechanisms of cell wall formation. In this study, we assembled de novo transcriptomes of three diatom species, Nitzschia palea, Achnanthes kuwaitensis, and Pseudoleyanella lunata, and compared protein-coding genes of five genome-sequenced diatom species. These analyses revealed a number of diatom-specific genes that encode putative endoplasmic reticulum-targeting proteins. Significant numbers of these proteins showed homology to silicanin-1, which is a conserved diatom protein that reportedly contributes to cell wall formation. These proteins also included a previously unrecognized SET domain protein methyltransferase family that may regulate functions of cell wall formation-related proteins and long-chain polyamines. Proteomic analysis of cell wall-associated proteins in N. palea identified a protein that is also encoded by one of the diatom-specific genes. Expression analysis showed that candidate genes were upregulated in response to silicon, suggesting that these genes play roles in silica cell wall formation. These candidate genes can facilitate further investigations of silica cell wall formation in diatoms

8-PN promotes recovery from muscle atrophy via Akt pathway

8-Prenylnaringenin (8-PN) is a prenylflavonoid that originates from hop extracts and is thought to help prevent disuse muscle atrophy. We hypothesized that 8-PN affects muscle plasticity by promoting muscle recovery under disuse muscle atrophy. To test the promoting effect of 8-PN on muscle recovery, we administered an 8-PN mixed diet to mice that had been immobilized with a cast to one leg for 14 days. Intake of the 8-PN mixed diet accelerated recovery from muscle atrophy, and prevented reductions in Akt phosphorylation. Studies on cell cultures of mouse myotubes in vitro demonstrated that 8-PN activated the PI3K/Akt/P70S6K1 pathway at physiologic concentrations. A cell-culture study using an inhibitor of estrogen receptors and an in vivo experiment with ovariectomized mice suggested that the estrogenic activity of 8-PN contributed to recovery from disuse muscle atrophy through activation of an Akt phosphorylation pathway. These data strongly suggest that 8-PN is a naturally occurring compound that could be used as a nutritional supplement to aid recovery from disuse muscle atrophy

Bioavailability of prenyl quercetin

Prenyl flavonoids are widely distributed in plant foods and have attracted appreciable attention in relation to their potential benefits for human health. Prenylation may enhance the biological functions of flavonoids by introducing hydrophobic properties in their basic structures. Previously, we found that 8-prenyl naringenin exerted a greater preventive effect on muscle atrophy than nonprenylated naringenin in a mouse model. Here, we aimed to estimate the effect of prenylation on the bioavailability of dietary quercetin (Q). The cellular uptake of 8-prenyl quercetin (PQ) and Q in Caco-2 cells and C2C12 myotube cells was examined. Prenylation significantly enhanced the cellular uptake by increasing the lipophilicity in both cell types. In Caco-2 cells, efflux of PQ to the basolateral side was <15% of that of Q, suggesting that prenylation attenuates transport from the intestine to the circulation. After intragastric administration of PQ or Q to mice or rats, the area under the concentration-time curve for PQ in plasma and lymph was 52.5% and 37.5% lower than that of Q, respectively. PQ and its O-methylated form (MePQ) accumulated at much higher amounts than Q and O-methylated Q in the liver (Q: 3400%; MePQ: 7570%) and kidney (Q: 385%; MePQ: 736%) of mice after 18 d of feeding. These data suggest that prenylation enhances the accumulation of Q in tissues during long-term feeding, even though prenylation per se lowers its intestinal absorption from the diet

ハイヨウセイ キン イシュク オ フセグ コウユビキチンカ ペプチド Cblin Cbl-b inhibitor ノ コウキノウカ

Skeletal muscle atrophy caused by unloading is characterized by both decreased responsiveness to myogenic growth factors and increased proteolysis. In our previous studies, it has been shown that ubiquitin ligase Cbl-b interacted and degraded the IGF-1 signaling intermediate IRS-1. We also reported that a peptide mimetic of tyrosin608-phosphorylated IRS-1 （DGpYMP）, named Cblin, Cbl-b inhibitor. However, Cblin may tend to be degraded by aminopeptidase in vivo. We aimed to confirm whether Cblin inhibiter muscle atrophy caused by glucocorticoids in mouse C2C12 myotubes, and effects of the modified Cblin N-terminus to prevent it from degradation. Pretreatment with Cblin significantly prevented the decrease in diameters of C2C12 myotubes treated with dexamethasone, and IRS-1 degradation, expression of atrogenes mRNA was repressed, and phosphorylation of Akt/mTOR was also protected. Moreover, the 50％ inhibitory concentration of N -myristoylated Cblin and Cblin for Cbl-b-mediated IRS-1 ubiquitination was 35μM and 120μM, respectively. In addition, N -myristoylated Cblin significantly inhibited the dexamethasone-induced reduction of myotube diameter. Taken together, these results suggest that Cblin Cblin prevented the dexamethasone induced myotube atrophy, and N -myristoyled Cblin is more effective than nonmodified Cblin in prevention of muscle atrophy

Ｎ末端へミリストイル化を施したCbl-bユビキチン化活性阻害剤は、グルココルチコイド誘導性の筋萎縮を抑制する。

A DGpYMP peptide mimetic of tyrosine608-phosphorylated insulin receptor substrate-1 (IRS-1), named Cblin, was previously shown to significantly inhibit Cbl-b-mediated IRS-1 ubiquitination. In the present study, we developed N-myristoylated Cblin and investigated whether it was effective in preventing glucocorticoid-induced muscle atrophy. Using HEK293 cells overexpressing Cbl-b, IRS-1 and ubiquitin, we showed that the 50% inhibitory concentrations of Cbl-b-mediated IRS-1 ubiquitination by N-myristoylated Cblin and Cblin were 30 and 120 μM, respectively. Regarding the DEX-induced atrophy of C2C12 myotubes, N-myristoylated Cblin was more effective than Cblin for inhibiting the DEX-induced decreases in C2C12 myotube diameter and IRS-1 degradation. The inhibitory efficacy of N-myristoylated Cblin on IRS-1 ubiquitination in C2C12 myotubes was approximately fourfold larger than that of Cblin. Furthermore, N-myristoylation increased the incorporation of Cblin into HEK293 cells approximately 10-folds. Finally, we demonstrated that N-myristoylated Cblin prevented the wet weight loss, IRS-1 degradation, and MAFbx/atrogin-1 and MuRF-1 expression in gastrocnemius muscle of DEX-treated mice approximately fourfold more effectively than Cblin. Taken together, these results suggest that N-myristoylated Cblin prevents DEX-induced skeletal muscle atrophy in vitro and in vivo, and that N-myristoylated Cblin more effectively prevents muscle atrophy than unmodified Cblin