Relationship of Low Vitamin B6 Status with Sarcopenia, Frailty, and Mortality: A Narrative Review.

Marginal vitamin B6 (B6) deficiency is a widespread global concern. Inadequate B6 levels have been linked to an increased risk of age-related chronic diseases such as cardiovascular diseases and cancers. In recent years, the growing concern over sarcopenia (the age-related loss of muscle mass and strength) and frailty (a decline in physiological resilience and increased vulnerability associated with aging) is particularly relevant due to the emergence of super-aged societies in developed countries. Notably, among the thirty-one studies included in this review, twenty-five showed a significant association of B6 status with sarcopenia, frailty, and all-cause mortality in adults (p < 0.05), while six showed no association. Emerging studies have suggested novel mechanisms underlying this association. These mechanisms involve P2X7 receptor-mediated NLRP3 inflammasome signaling, AMPK signaling, PD-L1 signaling, and satellite cell-mediated myogenesis. Furthermore, the modulation of PLP-dependent enzymes due to B6 deficiency is associated with impaired metabolic processes, affecting energy utilization, imidazole peptide production, and hydrogen sulfide production, as well as the kynurenine pathway, all of which play vital roles in skeletal muscle health and pathophysiology. This narrative review provides an up-to-date assessment of our current understanding of the potential role of nutritional B6 status in combating sarcopenia, frailty, and mortality.

Satellite cell content and muscle regeneration in a mouse model of NAFLD.

OBJECTIVES: Muscle wasting is a common complication in patients with nonalcoholic fatty liver disease (NAFLD). In this study, we investigated the effect of NAFLD on satellite cell (SC) content and skeletal muscle repair. METHODS: Male CD-1 mice fed a choline-deficient diet for 4 wk were used as an NAFLD model. We performed histologic and mRNA expression analyses, immunochemical staining with single muscle fibers to assess the effect of NAFLD on muscle Pax7+ SCs, and muscle regeneration by intramuscular injection of cardiotoxin. RESULTS: We found that the total number of Pax7+ SCs in the extensor digitorum longus and tibialis anterior muscles of mice with NAFLD was significantly decreased when compared with that in the control group, in which the depletion of the SC pool possibly impaired muscle regeneration, as evidenced by the smaller size of the regenerating myofibers. Importantly, we found that NAFLD significantly impaired the differentiation ability of SCs, as shown by a decreased number of SCs expressing a myogenic marker, MyoD. Finally, this study indicated that molecular mechanisms underlying a decline in SC numbers may be attributed to the upregulation of proinflammatory cytokines (tumor necrosis factor α [TNFα]) and an oxidative stress marker (NADPH oxidase-2 [NOX2\) in mice with NAFLD. CONCLUSIONS: The findings demonstrate that a decrease in SC content in the skeletal muscle is an important factor that contributes to muscle wasting in NAFLD. Thus, preservation of the muscle SC pool is a potential therapeutic strategy to reduce NAFLD-associated muscle wasting.

Emerging cardioprotective mechanisms of vitamin B6: a narrative review.

Although overt vitamin B6 deficiency is rare, marginal vitamin B6 deficiency is frequent and occurs in a consistent proportion of the population. The marginal vitamin B6 deficiency appears to relate to an increased risk of inflammation-related diseases, such as cardiovascular diseases and cancers. Of all the cardiovascular diseases, heart failure is a complex clinical syndrome associated with a high mortality rate. So far, information regarding the cardioprotective mechanisms of vitamin B6 has been limited. Meanwhile, recent studies have revealed that vitamin B6 treatment increases cardiac levels of imidazole dipeptides (e.g., carnosine, anserine, and homocarnosine), histamine, and γ-aminobutyric acid (GABA) and suppresses P2X7 receptor-mediated NLRP3 inflammasome. These modulations may imply potential cardioprotective mechanisms of vitamin B6. These modulations may also be involved in the underlying mechanisms through which vitamin B6 suppresses oxidative stress and inflammation. This review provides an up-to-date evaluation of our current understanding of the cardioprotective mechanisms of vitamin B6.

Comparative study on molecular mechanism of diabetic myopathy in two different types of streptozotocin-induced diabetic models.

AIMS: Streptozotocin (STZ)-induced diabetic animal models have been widely used to study diabetic myopathy; however, non-specific cytotoxic effects of high-dose STZ have been discussed. The purpose of this study was to compare diabetic myopathy in a high-STZ model with another well-established STZ model with reduced cytotoxicity (high-fat diet (HFD) and low-dose STZ) and to identify mechanistic insights underlying diabetic myopathy in STZ models that can mimic perturbations observed in human patients with diabetic myopathy. MAIN METHODS: Male C57BL6 mice were injected with a single high dose of STZ (180 mg/kg, High-STZ) or were given HFD plus low-dose STZ injection (STZ, 55 mg/kg/day, five consecutive days, HFD/STZ). We characterized diabetic myopathy by histological and immunochemical analyses and conducted gene expression analysis. KEY FINDINGS: The high-STZ model showed a significant reduction in tibialis anterior myofiber size along with decreased satellite cell content and downregulation of inflammation response and collagen gene expression. Interestingly, blood corticosteroid levels were significantly increased in the high-STZ model, which was possibly related to lowered inflammation response-related gene expression. Further analyses using the HFD/STZ model showed downregulation of gene expression related to mitochondrial functions accompanied by a significant decrease in ATP levels in the muscles. SIGNIFICANCE: The high-STZ model is suitable for studies regarding not only severe diabetic myopathy with excessive blood glucose but also negative impact of glucocorticoids on skeletal muscles. In contrast, the HFD/STZ model is characterized by higher immune responses and lower ATP production, which also reflects the pathologies observed in human diabetic patients.

Fermented date residue extract mix containing gamma-aminobutyric acid augments the immune function of mouse splenocytes.

An extract of date (fruit of a palm tree) residue plus food-grade glutamate, acetic acid, and yeast extract (date residue extract mix, DREM) has been successfully fermented with using Lactobacillus brevis JCM 1059T to produce gamma-aminobutyric acid (GABA). Here, mouse splenocytes were found to be viable when supplemented with DREM and fermented DREM containing GABA (fDREM). The addition of DREM and fDREM resulted in the secretion of tumor necrosis factor (TNF)-α from the splenocytes, fDREM being more effective than DREM. The TNF-α secretion with DREM was elevated by exogenous addition of GABA and that with fDREM was in part mediated via A-type GABA receptors. Contrary to general understanding of the suppressive effects of GABA on various biological functions, our findings suggest that GABA-containing fDREM arguments the immune function as a food and pharmaceutical material.

Consumption of Low-Dose of Ethanol Suppresses Colon Tumorigenesis in 1,2-Dimethylhydrazine-Treated Rats.

The effect of low-dose of ethanol consumption on the development of colon cancer is unclear. This study aimed to investigate the effects of low-dose ethanol (0.5%, 1%, and 2% [v/v] ethanol in drinking water) for 28 wk on colon tumor incidence in rats injected with 1,2-dimethylhydrazine. Body weight, fluid and food consumption, and the total numbers of colon adenomas (mild-, moderate-, and severe-grade dysplasia) per rat were unaffected by ethanol consumption. However, the numbers of severe-grade dysplasia were significantly reduced by 1% ethanol compared with the control (0% ethanol; -93%) but not by 0.5% and 2% ethanol. Although the numbers of total adenocarcinomas were unaffected, those of total of adenomas and adenocarcinomas together were significantly reduced by 0.5% and 1% ethanol (-39% and -41%, respectively). Intriguingly, real-time PCR assay indicated the abundance of cecal Clostridium leptum (a putative immunosuppressor) was the least in rats received 1% ethanol. Furthermore, 1% ethanol markedly increased colonic mRNA of IL-6, a putative suppressor of regulatory T-cells and cytoprotector. This study provides the first evidence for the potential of 1% ethanol, but not 2% ethanol, to prevent colon tumorigenesis in rats, supporting the J-curve hypothesis of the effect of low-dose alcohol on health. Further, the modulation of C. leptum and expression of IL-6, potentially linking to carcinogenesis, by 1% ethanol may provide an insight into the underlying mechanisms of the anti-colon tumor effect.

The serum amyloid A3 promoter-driven luciferase reporter mice is a valuable tool to image early renal fibrosis development and shows the therapeutic effect of glucosyl-hesperidin treatment.

Tubulointerstitial fibrosis is a progressive process affecting the kidneys, causing renal failure that can be life-threatening. Thus, renal fibrosis has become a serious concern in the ageing population; however, fibrotic development cannot be diagnosed early and assessed noninvasively in both patients and experimental animal models. Here, we found that serum amyloid A3 (Saa3) expression is a potent indicator of early renal fibrosis; we also established in vivo Saa3/C/EBPß-promoter bioluminescence imaging as a sensitive and specific tool for early detection and visualization of tubulointerstitial fibrosis. Saa3 promoter activity is specifically upregulated in parallel with tumor necrosis factor α (TNF-α) and fibrotic marker collagen I in injured kidneys. C/EBPß, upregulated in injured kidneys and expressed in tubular epithelial cells, is essential for the increased Saa3 promoter activity in response to TNF-α, suggesting that C/EBPß plays a crucial role in renal fibrosis development. Our model successfully enabled visualization of the suppressive effects of a citrus flavonoid derivative, glucosyl-hesperidin, on inflammation and fibrosis in kidney disease, indicating that this model could be widely used in exploring therapeutic agents for fibrotic diseases.

Feeding Aspergillus protease preparation combined with adequate protein diet to rats increases levels of cecum gut-protective amino acids, partially linked to Bifidobacterium and Lactobacillus.

Our recent study indicated that dietary Aspergillus oryzae-derived protease preparation (AP), through its enzymatic activity, exerted a bifidogenic effect in rats. We hypothesized that dietary AP links to protein degradation and subsequently elevates gut-protective amino acids (AAs) in rats fed adequate protein diet. In this study, dietary AP markedly increased the relative abundance of Bifidobacterium and Lactobacillus and the levels of free threonine, alanine, proline, taurine, ornithine, phenylalanine, cystine, and γ-aminobutyric acid in the cecum contents of rats fed with an adequate protein diet, but not in those fed with a low-protein diet. The elevated AAs, except ornithine and phenylalanine, potentially have gut-related health benefits. Some of the AP-modulated free AAs appeared to be associated with the relative abundance of Bifidobacterium and Lactobacillus. Thus, AP combined with adequate protein diet is likely to increase the levels of cecum beneficial free AAs, which is partially associated with the relative abundance of the probiotics.

Transgenic mice specifically expressing amphiregulin in white adipose tissue showed less adipose tissue mass.

To determine adipocytokines that play a regulatory role during obesity development, we explored the genes that encode growth factors and investigated the physiological functions for adipose tissue development. Here, we isolated amphiregulin (Areg) gene whose expression was significantly up-regulated in obese adipose tissues. Areg mRNA level was positively correlated with macrophage marker gene expression in adipose tissues in vivo. Unexpectedly, Areg transgenic mice showed less adipose tissue mass with increased mRNA expression levels of Tnf-α and peroxisome proliferator-activated receptor γ coactivator 1α (Pgc-1α) and delayed white adipose tissue development during the convalescent stage in a dextran sodium sulfate-induced colitis model. This study showed that Areg mRNA expression was significantly up-regulated in obese adipose tissues and over-expression of Areg in white adipose tissue caused less adipose tissue mass.

Feeding of the water extract from Ganoderma lingzhi to rats modulates secondary bile acids, intestinal microflora, mucins, and propionate important to colon cancer.

Consumption of reishi mushroom has been reported to prevent colon carcinogenesis in rodents, although the underlying mechanisms remain unclear. To investigate this effect, rats were fed a high-fat diet supplemented with 5% water extract from either the reishi mushroom (Ganoderma lingzhi) (WGL) or the auto-digested reishi G. lingzhi (AWGL) for three weeks. Both extracts markedly reduced fecal secondary bile acids, such as lithocholic acid and deoxycholic acid (colon carcinogens). These extracts reduced the numbers of Clostridium coccoides and Clostridium leptum (secondary bile acids-producing bacteria) in a per g of cecal digesta. Fecal mucins and cecal propionate were significantly elevated by both extracts, and fecal IgA was significantly elevated by WGL, but not by AWGL. These results suggest that the reishi extracts have an impact on colon luminal health by modulating secondary bile acids, microflora, mucins, and propionate that related to colon cancer.

Identification of peptides in wheat germ hydrolysate that demonstrate calmodulin-dependent protein kinase II inhibitory activity.

Hydrolysis of wheat germ by proteases resulted in bioactive peptides that demonstrated an inhibitory effect against the vasoconstrictive Ca(2+)-calmodulin (CaM)-dependent protein kinase II (CaMK II). The hydrolysate by thermolysin (1.0wt%, 5h) showed a particularly potent CaMK II inhibition. As a result of mixed mode high-performance liquid chromatography of thermolysin hydrolysate with pH elution gradient ranging between 4.8 and 8.9, the fraction eluted at pH 8.9 was the most potent CaMK II inhibitor. From this fraction, Trp-Val and Trp-Ile were identified as CaMK II inhibitors. In Sprague-Dawley rats, an enhanced aortic CaMK II activity by 1µM phenylephrine was significantly (p<0.05) suppressed by 15-min incubation with 300µM Trp-Val or Trp-Ile. On the basis of Ca(2+)-chelating fluorescence and CaMK II activity assays, it was concluded that Trp-Val and Trp-Ile competed with Ca(2+)-CaM complex to bind to CaMK II with Ki values of 5.4 and 3.6µM, respectively.

Vasorelaxant Effect of 5'-Methylthioadenosine Obtained from Candida utilis Yeast Extract through the Suppression of Intracellular Ca(2+) Concentration in Isolated Rat Aorta.

Our study is the first to demonstrate the vasorelaxant effect of Candida utilis yeast extract on rat aorta (EC50 of 7.2 ± 3.2 mg/mL). Among five identified compounds, 5'-methylthioadenosine (MTA) exhibited comparable vasorelaxant effect (EC50 of 190 ± 40 µM) with adenosine, a known vasodilator, on 1 µM phenylephrine (PE)-contracted Sprague-Dawley rat aortic rings. MTA induced vasorelaxation in an endothelium-independent manner and independent of the adenosine receptors. MTA reduced a CaCl2-induced vasocontraction stimulated by 1 µM PE, whereas the effect was abolished in a 60 mM KCl-induced vasocontraction. This indicates that MTA was not involved in the suppression of extracellular Ca(2+) influx. MTA significantly (P < 0.01) attenuated the PE-induced activation of calmodulin-dependent kinase II (CaMK II) in aortic rings and inhibited the phosphorylation of L-type Ca(2+) channel (VDCC). In conclusion, the underlying mechanism(s) of MTA-induced vasorelaxation involves the inhibition of Ca(2+)/CaMK II/VDCC phosphorylation pathway, resulting in the suppression of intracellular Ca(2+) concentration in aortic rings.

Identification of peptides from soybean protein, glycinin, possessing suppression of intracellular Ca2+ concentration in vascular smooth muscle cells.

In this study, we challenged to identify vasoactive peptides in soybean 11S glycinin hydrolysate by thermolysin to regulate intracellular Ca(2+) concentration ([Ca(2+)]i) that can induce constrictive vascular tension. As a function of the inhibition of elevated [Ca(2+)]i by 10 µM angiotensin (Ang) II in vascular smooth muscle cells (VSMCs), eleven peptides were successfully identified from the hydrolysate, among which His-Gly-Lys exhibited the most potent inhibition against [Ca(2+)]i elevation in Ang II-stimulated VSMCs (inhibition at 300 µM: 46.5±8.0% vs. control). The biological capacity of His-Gly-Lys analogues as an [Ca(2+)]i inhibitor was also proven when His-Lys and His-Gly-Arg elicited a significant reduction in [Ca(2+)]i. In contrast, less reduction of [Ca(2+)]i by His-Gly-Ile and His-(3-methyl)-Gly-Lys indicated the importance of the imino proton in His, along with basic amino acids positioned at C-terminal for the effect.