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.

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.

Vitamin B6 Prevents IL-1ß Protein Production by Inhibiting NLRP3 Inflammasome Activation.

Vitamin B6 includes six water-soluble vitamers: pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), and their phosphorylated forms. Pyridoxal 5'-phosphate (PLP) is an important cofactor for many metabolic enzymes. Several lines of evidence demonstrate that blood levels of PLP are significantly lower in patients with inflammation than in control subjects and that vitamin B6 has anti-inflammatory effects, with therapeutic potential for a variety of inflammatory diseases. Although one of our group previously demonstrated that PL inhibits the NF-κB pathway, the molecular mechanism by which vitamin B6 suppresses inflammation is not well understood. Here, we showed that both PL and PLP suppressed the expression of cytokine genes in macrophages by inhibiting Toll-like receptor (TLR)-mediated TAK1 phosphorylation and the subsequent NF-κB and JNK activation. Furthermore, PL and PLP abolished NLRP3-dependent caspase-1 processing and the subsequent secretion of mature IL-1ß and IL-18 in LPS-primed macrophages. In contrast, PM and PN had little effect on IL-1ß production. PLP, but not PL, markedly reduced the production of mitochondrial reactive oxygen species (ROS) in peritoneal macrophages. Importantly, PL and PLP reduced IL-1ß production induced by LPS and ATP, or by LPS alone, in mice. Moreover, PL and PLP protected mice from lethal endotoxic shock. Collectively, these findings reveal novel anti-inflammatory activities for vitamin B6 and suggest its potential for preventing inflammatory diseases driven by the NLRP3 inflammasome.

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.

New members of the mammalian glycerophosphodiester phosphodiesterase family: GDE4 and GDE7 produce lysophosphatidic acid by lysophospholipase D activity.

The known mammalian glycerophosphodiester phosphodiesterases (GP-PDEs) hydrolyze glycerophosphodiesters. In this study, two novel members of the mammalian GP-PDE family, GDE4 and GDE7, were isolated, and the molecular basis of mammalian GP-PDEs was further explored. The GDE4 and GDE7 sequences are highly homologous and evolutionarily close. GDE4 is expressed in intestinal epithelial cells, spermatids, and macrophages, whereas GDE7 is particularly expressed in gastro-esophageal epithelial cells. Unlike other mammalian GP-PDEs, GDE4 and GDE7 cannot hydrolyze either glycerophosphoinositol or glycerophosphocholine. Unexpectedly, both GDE4 and GDE7 show a lysophospholipase D activity toward lysophosphatidylcholine (lyso-PC). We purified the recombinant GDE4 and GDE7 proteins and show that these enzymes can hydrolyze lyso-PC to produce lysophosphatidic acid (LPA). Further characterization of purified recombinant GDE4 showed that it can also convert lyso-platelet-activating factor (1-O-alkyl-sn-glycero-3-phosphocholine; lyso-PAF) to alkyl-LPA. These data contribute to our current understanding of mammalian GP-PDEs and of their physiological roles via the control of lyso-PC and lyso-PAF metabolism in gastrointestinal epithelial cells and macrophages.

Hypolipidemic activity of common (Fagopyrum esculentum Moench) and tartary (Fagopyrum tataricum Gaertn.) buckwheat.

Buckwheat grain has well-balanced nutritional value, whereas its digestibility is relatively low. This review summarizes recent advances in studies on the hypolipidemic activity of buckwheat. The most remarkable function is a powerful hypocholesterolemic activity of buckwheat protein in rats, which is far stronger than that of soy protein. The cholesterol-lowering effect is mediated by mechanisms involving higher excretion of fecal sterols and lower digestibility of buckwheat protein. The insoluble fraction of buckwheat protein associates with cholesterol and reduces micelle cholesterol uptake in caco-2 cells. Furthermore, consumption of buckwheat protein suppresses cholesterol-induced gallstones and body fat in rodents. Buckwheat sprouts also have hypolipidemic activity in rats or type 2 diabetic mice. Tartary buckwheat bran extract reduced the serum level of total cholesterol and triglyceride in hyperlipidemic rats. The consumption of buckwheat seed reduced low-density lipoprotein cholesterol in the pastureland Mongolian population. Taken together, buckwheat may be beneficial for prevention of hyperlipidemia.

IκB kinase epsilon expression in adipocytes is upregulated by interaction with macrophages.

Macrophage infiltration in the adipose tissue, and the interaction with adipocytes, is well documented to be involved in fat inflammation and obesity-associated complications. In this study, we isolated IκB kinase ε (IKKε) as a key adipocyte factor that is potentially affected by interaction with macrophages in adipose tissue in vivo. We showed that IKKε mRNA expression levels in white adipose tissue were increased in both genetic and diet-induced obese mouse. Furthermore, IKKε mRNA expression was decreased by the administration of vitamin B6, an anti-inflammatory vitamin, and that IKKε expression levels in adipose tissue were closely correlated with the numbers of infiltrating macrophages. In a co-culture system, we showed that IKKε expression in adipocytes was upregulated by interaction with activated macrophages. This study provides novel insight into IKKε, which is involved in adipose tissue inflammation during the development of obesity.

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.

Burdock fermented by Aspergillus awamori elevates cecal Bifidobacterium, and reduces fecal deoxycholic acid and adipose tissue weight in rats fed a high-fat diet.

This study investigated the effects of dietary supplementation with burdock powder and Aspergillus awamori-fermented burdock powder at 5% on the intestinal luminal environment and body fat in rats fed a high-fat (HF) diet. Food intake and growth were unaffected by dietary manipulation. Consumption of the burdock and fermented burdock diets significantly elevated fecal IgA and mucins (indices of intestinal immune and barrier functions) and reduced fecal lithocholic acid (a risk factor for colon cancer) (p<0.05). The fermented burdock diet markedly elevated cecal Bifidobacterium and organic acids, including lactate, acetate, propionate, and butyrate, and reduced fecal deoxycholic acid (a risk factor for colon cancer) and perirenal adipose tissue weight (p<0.05), but the burdock diet did not. These results suggest that consumption of fermented burdock improves the intestinal luminal environment and suppresses obesity in rats fed a HF diet.

Tempe consumption modulates fecal secondary bile acids, mucins, immunoglobulin A, enzyme activities, and cecal microflora and organic acids in rats.

The present study investigated the effect of dietary tempe, a fermented soy product, on the colonic environment of rats fed high-fat (HF, 30 % fat; experiment 1) or low-fat (LF, 6 % fat; experiment 2) diets. Growing male rats were fed the experimental diets with or without 25 % tempe for 21 days. Tempe consumption slightly but significantly increased the growth of rats fed both the HF and LF diets (P < 0.05). With both the HF and LF diets, dietary tempe markedly reduced a harmful fecal secondary bile acid, lithocholic acid (a risk factor of colon cancer) (P < 0.05), and markedly elevated fecal mucins (indices of intestinal barrier function) and immunoglobulin A (IgA, an index of intestinal immune function) (P < 0.05). With the HF diet, dietary tempe increased cecal acetate, butyrate, propionate, and succinate concentrations (P < 0.05). Analysis of the profile of cecal microflora revealed lower Bacteroides and higher Clostridium cluster XIVa levels in the tempe group of rats fed the HF diet (P < 0.05). Compared with the control group, the fecal activity of ß-glucosidase was markedly higher in the tempe group (P < 0.05), while that of urease was lower (P < 0.05) with both the HF and LF diets. The present results suggest that tempe consumption modulates the colonic environment in rats.

A novel glycerophosphodiester phosphodiesterase, GDE5, controls skeletal muscle development via a non-enzymatic mechanism.

Mammalian glycerophosphodiester phosphodiesterases (GP-PDEs) have been identified recently and shown to be implicated in several physiological functions. This study isolated a novel GP-PDE, GDE5, and showed that GDE5 selectively hydrolyzes glycerophosphocholine (GroPCho) and controls skeletal muscle development. We show that GDE5 expression was reduced in atrophied skeletal muscles in mice and that decreasing GDE5 abundance promoted myoblastic differentiation, suggesting that decreased GDE5 expression has a counter-regulatory effect on the progression of skeletal muscle atrophy. Forced expression of full-length GDE5 in cultured myoblasts suppressed myogenic differentiation. Unexpectedly, a truncated GDE5 construct (GDE5DeltaC471), which contained a GP-PDE sequence identified in other GP-PDEs but lacked GroPCho phosphodiesterase activity, showed a similar inhibitory effect. Furthermore, transgenic mice specifically expressing GDE5DeltaC471 in skeletal muscle showed less skeletal muscle mass, especially type II fiber-rich muscle. These results indicate that GDE5 negatively regulates skeletal muscle development even without GroPCho phosphodiesterase activity, providing novel insight into the biological significance of mammalian GP-PDE function in a non-enzymatic mechanism.

Consumption of a resistant protein, sericin, elevates fecal immunoglobulin A, mucins, and cecal organic acids in rats fed a high-fat diet.

We previously reported that consumption of a resistant protein, sericin, reduces colon tumorigenesis, constipation, and serum TG in rodents. The present study was conducted to elucidate the effects of dietary sericin on the intestinal luminal environment in rats fed a high-fat (HF) diet. Rats were fed 300 or 50 g/kg of beef tallow with or without 40 g/kg sericin, a protein purified from cocoons of Bombix mori, for 3 wk. Intestinal luminal variables, including IgA (index of intestinal immune function), mucins (index of barrier function), organic acids, microflora, and secondary bile acids, were measured. Dietary sericin markedly elevated fecal IgA in the HF diet group (3-fold, P < 0.05) but not in the low-fat (LF) diet group. Fecal mucin levels were elevated by sericin intake in the HF diet group (P < 0.05). Cecal organic acids, including acetate, propionate, n-butyrate, and succinate, were significantly lower in the HF diet group compared with the LF diet group. Dietary sericin significantly elevated cecal acetate and n-butyrate in the HF diet group but not in the LF diet group. Compared with the LF diet, the HF diet significantly increased serum TG in the untreated group but not in those fed sericin. The HF diet increased lower density lipoprotein (VLDL + IDL + LDL) cholesterol and it was reduced by sericin intake (P < 0.05). There was an inverse correlation between serum TG and cecal acetate (Spearman rank correlation coefficient = -0.63; P < 0.001). The profile of microflora in cecal digesta and fecal secondary bile acids (a risk factor for colon cancer) did not differ between the HF diet and HF diet with sericin groups. These results suggest a novel and favorable effect of sericin on colon health by modulating intestinal immune and barrier functions and fermentation in rats fed a HF diet.

Fish oil feeding up-regulates the expression of 5-aminolevulinate synthase 2 mRNA in rat brain.

In this study, we investigated the effect of fish oil on gene expression in the cerebral cortex, and found that 5-aminolevulinate synthase 2 (ALAS2) mRNA expression was up-regulated by fish oil feeding. ALAS2 promoter activity was found to be regulated by retinoic acid. Our results suggest that fish oil modulates neuronal functions via heme synthesis.

The developmentally regulated osteoblast phosphodiesterase GDE3 is glycerophosphoinositol-specific and modulates cell growth.

The glycerophosphodiester phosphodiesterase enzyme family involved in the hydrolysis of glycerophosphodiesters has been characterized in bacteria and recently identified in mammals. Here, we have characterized the activity and function of GDE3, one of the seven mammalian enzymes. GDE3 is up-regulated during osteoblast differentiation and can affect cell morphology. We show that GDE3 is a glycerophosphoinositol (GroPIns) phosphodiesterase that hydrolyzes GroPIns, producing inositol 1-phosphate and glycerol, and thus suggesting specific roles for this enzyme in GroPIns metabolism. Substrate specificity analyses show that wild-type GDE3 selectively hydrolyzes GroPIns over glycerophosphocholine, glycerophosphoethanolamine, and glycerophosphoserine. A single point mutation in the catalytic domain of GDE3 (GDE3R231A) leads to loss of GroPIns enzymatic hydrolysis, identifying an arginine residue crucial for GDE3 activity. After heterologous GDE3 expression in HEK293T cells, phosphodiesterase activity is detected in the extracellular medium, with no effect on the intracellular GroPIns pool. Together with the millimolar concentrations of calcium required for GDE3 activity, this predicts an enzyme topology with an extracellular catalytic domain. Interestingly, GDE3 ectocellular activity is detected in a stable clone from a murine osteoblast cell line, further confirming the activity of GDE3 in a more physiological context. Finally, overexpression of wild-type GDE3 in osteoblasts promotes disassembly of actin stress fibers, decrease in growth rate, and increase in alkaline phosphatase activity and calcium content, indicating a role for GDE3 in induction of differentiation. Thus, we have identified the GDE3 substrate GroPIns as a candidate mediator for osteoblast proliferation, in line with the GroPIns activity observed previously in epithelial cells.

Inhibitory effect of curcumin on IMP dehydrogenase, the target for anticancer and antiviral chemotherapy agents.

Inosine monophosphate dehydrogenase (IMPDH), a rate-limiting enzyme in the de novo synthesis of guanine nucleotides, is a therapeutic target for anticancer and antiviral agents. Among the 15 different polyphenols examined, curcumin was found to have an inhibitory effect on the IMPDH activity in both a competitive and uncompetitive manner and to suppress the cellular GTP level in HT-29 colon carcinoma cells.

Consumption of sericin reduces serum lipids, ameliorates glucose tolerance and elevates serum adiponectin in rats fed a high-fat diet.

The effect was examined of dietary sericin on the lipid and carbohydrate metabolism in rats fed with a high-fat diet. The rats were fed with a 20% beef tallow diet with or without sericin at the level of 4% for 5 weeks. The final body weight and white adipose tissue weight were unaffected by dietary manipulation. The consumption of sericin significantly reduced the serum levels of triglyceride, cholesterol, phospholipids and free fatty acids. Serum very-low-density lipoprotein (VLDL)-triglyceride, VLDL-cholesterol, low-density lipoprotein (LDL)-cholesterol and LDL-phospholipids were also significantly reduced by the sericin intake. Liver triglyceride and the activities of glucose 6-phosphate dehydrogenase and malic enzyme, the lipogenic enzymes, were also reduced by the sericin intake. Dietary sericin caused a marked elevation in serum adiponectin. The consumption of sericin suppressed the increases in plasma glucose and insulin levels after an intraperitoneal glucose injection. These results imply the usefulness of sericin for improving the lipid and carbohydrate metabolism in rats fed on a high-fat diet.

Low-Dose Ethanol Has Impacts on Plasma Levels of Metabolites Relating to Chronic Disease Risk in SAMP8 mice.

The effects of low-dose alcohol on experimental animals are unclear. This study examined plasma metabolites in senescence-accelerated mice 8 (SAMP8) given low-dose ethanol, and compared them with aging progress and skeletal muscle strength. Male SAMP8 mice (10-wk-old) were given drinking water containing 0% (control), 1%, 2%, or 5% (v/v) ethanol for 14 wk. Compared with the control group, only mice who consumed 1% ethanol experienced a lower senescence score at 18 and 23 wk, as well as an increased limb grip strength at 21 wk. Plasma metabolites of control, 1% and 2% ethanol groups were analyzed by capillary electrophoresis-time-of-flight mass spectrometry (CE-TOF/MS). Among the 7 metabolites affected by ethanol, notewhorthy is the positive association of the ethanol levels in drinking water with the levels of α-ketoglutarate (antioxidant and anti-inflammatory metabolite) and hippurate (antioxidant and microbial co-metabolite) (p<0.05). Intriguingly, the levels of 2-hydroxyisobutyrate (the biomarker of energy metabolism and microbial co-metabolite) were higher in the 1% ethanol group (p<0.05), but not in the 2% ethanol group as compared to the control. Furthermore, the levels of some of the metabolites affected were correlated with some variables in the grading score of senescence and muscle strength. This study provides a novel insight into how low-dose ethanol in SAMP8 mice modulates the levels of circulating metabolites relating to chronic disease risk.

Generation of a zinc finger protein ZPR1 mutant that constitutively interacted with translation elongation factor 1alpha.

Zinc finger protein ZPR1 (ZPR1) binds to eukaryotic translation elongation factor 1alpha (eEF1alpha) in response to growth stimuli, and is also involved in transcription and cell cycle regulation. In this study, we characterized the interaction of ZPR1 and eEF1alpha and generated a ZPR1 mutant that constitutively interacted with eEF1alpha. ZPR1-DeltaA (Delta193-246) bound to eEF1alpha independently of Zn(2+) in vivo. This study indicates that ZPR1-DeltaA (Delta193-246) is a useful tool to provide structural insights into ZPR1 and to investigate the biological significance of the interaction between ZPR1 and eEF1alpha.

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.

Novel metabolic disturbances in marginal vitamin B6-deficient rat heart.

Vitamin B6 deficiency is associated with cardiovascular disease (CVD). Although plasma biomarkers have been proposed, no studies have yet directly profiled heart tissue, and the mechanisms have to be fully defined. Thus, in order to provide better insight into vitamin B6-deficient effects on cardiac functions, we sought to identify the metabolic profile in heart tissue consequent to change in dietary vitamin B6 levels by applying metabolomics. Heart tissues of rats fed a basal diet containing a marginal vitamin B6-deficient, vitamin B6-recommended or vitamin B6-supplemented level were analyzed by metabolomics analysis. Among over 500 detected metabolites, imidazole metabolites including carnosine, anserine, homocarnosine and histamine exhibited the highest decrease upon vitamin B6 deficiency (>-45%, P<.01), along with their precursors ß-alanine, γ-aminobutyric acid (GABA) and 1-methylhistidine. Ornithine was the only metabolite exhibiting an increased level in the vitamin B6-deficient group. Vitamin B6 deficiency significantly attenuated the activity of heart tissue glutamate decarboxylase (GAD), although there was undetectable activity of aspartate decarboxylase (ADC), suggesting that the involvement of vitamin B6 in imidazole metabolite synthesis occurs partly through GABA production by regulating GAD rather than through a straightforward ß-alanine production pathway via ADC in the heart. Notably, vitamin B6 deficiency significantly attenuated citric acid cycle metabolite levels, suggesting cardiac energy metabolism impairment. This study provides a new link between vitamin B6 and cardiac functions, in which marginal vitamin B6 deficiency impairs imidazole and energy metabolism in heart. This newly revealed cardiac metabolic profile may reveal novel molecular targets or foodstuffs for CVD prevention.