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.

Satellite Cells Exhibit Decreased Numbers and Impaired Functions on Single Myofibers Isolated from Vitamin B6-Deficient Mice.

Emerging research in human studies suggests an association among vitamin B6, sarcopenia, and muscle strength. However, very little is known regarding its potential role at the cellular level, especially in muscle satellite cells. Therefore, to determine whether vitamin B6 affects the satellite cells, we isolated single myofibers from muscles of vitamin B6-deficient and vitamin B6-supplemented mice. Subsequently, we subjected them to single myofiber culture and observed the number and function of the satellite cells, which remained in their niche on the myofibers. Prior to culture, the vitamin B6-deficient myofibers exhibited a significantly lower number of quiescent satellite cells, as compared to that in the vitamin B6-supplemented myofibers, thereby suggesting that vitamin B6 deficiency induces a decline in the quiescent satellite cell pool in mouse muscles. After 48 and 72 h of culture, the number of proliferating satellite cells per cluster was similar between the vitamin B6-deficient and -supplemented myofibers, but their numbers decreased significantly after culturing the myofibers in vitamin B6-free medium. After 72 h of culture, the number of self-renewing satellite cells per cluster was significantly lower in the vitamin B6-deficient myofibers, and the vitamin B6-free medium further decreased this number. In conclusion, vitamin B6 deficiency appears to reduce the number of quiescent satellite cells and suppress the proliferation and self-renewal of satellite cells during myogenesis.

Molecular docking and pharmacokinetic studies of phytocompounds from Nigerian Medicinal Plants as promising inhibitory agents against SARS-CoV-2 methyltransferase (nsp16).

BACKGROUND: Since the index case was reported in China, COVID-19 has led to the death of at least 4 million people globally. Although there are some vaccine cocktails in circulation, the emergence of more virulent variants of SARS-CoV-2 may make the eradication of COVID-19 more difficult. Nsp16 is an S-adenosyl-L-Methionine-dependent methyltransferase that plays an important role in SARS-CoV-2 viral RNA cap formation-a crucial process that confers viral stability and prevents virus detection by cell innate immunity mechanisms. This unique property makes nsp16 a promising molecular target for COVID-19 drug design. Thus, this study aimed to identify potent phytocompounds that can effectively inhibit SARS-CoV-2 nsp16. We performed in silico pharmacokinetic screening and molecular docking studies using 100 phytocompounds-isolated from fourteen Nigerian plants-as ligands and nsp16 (PDB: 6YZ1) as the target. RESULTS: We found that only 59 phytocompounds passed the drug-likeness analysis test. However, after the docking analysis, only six phytocompounds (oxopowelline, andrographolide, deacetylbowdensine, 11, 12-dimethyl sageone, sageone, and quercetin) isolated from four Nigerian plants (Crinum jagus, Andrographis paniculata, Sage plants (Salvia officinalis L.), and Anacardium occidentale) showed good binding affinity with nsp16 at its active site with docking score ranging from - 7.9 to - 8.4 kcal/mol. CONCLUSIONS: Our findings suggest that the six phytocompounds could serve as therapeutic agents to prevent viral survival and replication in cells. However, further studies on the in vitro and in vivo inhibitory activities of these 6 hit phytocompounds against SARS-CoV-2 nsp16 are needed to confirm their efficacy and dose.

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.

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.

Gender Difference and Dietary Supplemental Vitamin B6: Impact on Colon Luminal Environment.

Colon diseases can be affected by several factors such as gender difference and dietary supplemental vitamin B6 (B6). The nutritional status of B6 is affected by gender difference, leading us to hypothesize that gender difference affects colon luminal environment, which is dependent on B6 status. To investigate this hypothesis, we fed male and female rats a diet containing 1 mg, 7 mg, or 35 mg pyridoxine HCl/kg diet for 6 wk. We found significantly higher fecal mucin levels in female rats compared to those in male rats. Supplemental B6 significantly increased fecal mucins and was particularly profound in the female rats. The abundances of cecal and fecal Akkermansia muciniphila (mucin degrader) were unaffected. The fecal mucin levels were significantly correlated with colonic free threonine and serine and with gene expression of colon MUC16, implying that the combined effect of gender and dietary B6 on fecal mucins was mediated by the alteration in the levels of such amino acids and MUC16 expression. This study further showed the significant effects of gender difference on colonic free amino acids such as threonine, ornithine, asparagine/aspartate ratio, and glutamine/glutamate ratio, cecal and fecal Lactobacillus spp. levels, and colonic gene expressions of MUC16 and TLR8, the factors relating to colon health and diseases. Therefore, our findings suggest that gender difference and dietary B6 may have an impact on colon diseases by modulating these parameters.

Dietary vitamin B6 modulates the gene expression of myokines, Nrf2-related factors, myogenin and HSP60 in the skeletal muscle of rats.

Previous studies have suggested that vitamin B6 is an ergogenic factor. However, the role of dietary vitamin B6 in skeletal muscle has not been widely researched. The aim of the present study was to investigate the effects of dietary vitamin B6 on the gene expression of 19 myokines, 14 nuclear factor erythroid 2-related factor 2 (Nrf2)-regulated factors, 8 myogenesis-related factors and 4 heat shock proteins (HSPs), which may serve important roles in skeletal muscles. Rats were fed a diet containing 1 (marginal vitamin B6 deficiency), 7 (recommended dietary level) or 35 mg/kg of pyridoxine (PN) HCl/ for 6 weeks. Gene expressions were subsequently analysed using reverse transcription-quantitative polymerase chain reaction. Food intake and growth were unaffected by this dietary treatment. The rats in the 7 and 35 mg/kg PN HCl groups exhibited a significant increase in the concentration of pyridoxal 5'-phosphate in the gastrocnemius muscle compared with the 1 mg/kg PN HCl diet (P<0.01). The expressions of myokines, such as IL-7, IL-8, secreted protein acidic and rich in cysteine, IL-6, growth differentiation factor 11, myonectin, leukaemia inhibitory factor, apelin and retinoic acid receptor responder (tazarotene induced) 1, the expression of Nrf2 and its regulated factors, such as heme oxygenase 1, superoxide dismutase 2, glutathione peroxidase 1 and glutathione S-transferase, and the expression of myogenin and HSP60 were significantly elevated in the 7 mg/kg PN HCl group compared with the 1 mg/kg PN HCl diet (P<0.05). No significant differences in levels of these genes were observed between the 35 and 1 mg/kg PN HCl, with the exception of GDF11 and myonectin, whose expressions were significantly increased in the 35 mg/kg PN HCl (P<0.05). Notably, the majority of gene expressions that were affected responded to dietary supplemental vitamin B6 in a similar manner. The results suggest that compared with the marginal vitamin B6 deficiency, the recommended dietary intake of vitamin B6 upregulates the gene expression of a number of factors that promote the growth and repair of skeletal muscle.

Molecular characterization of aspartylglucosaminidase, a lysosomal hydrolase upregulated during strobilation in the moon jellyfish, Aurelia aurita.

The life cycle of the moon jellyfish, Aurelia aurita, alternates between a benthic asexual polyp stage and a planktonic sexual medusa (jellyfish) stage. Transition from polyp to medusa is called strobilation. To investigate the molecular mechanisms of strobilation, we screened for genes that are upregulated during strobilation using the differential display method and we identified aspartylglucosaminidase (AGA), which encodes a lysosomal hydrolase. Similar to AGAs from other species, Aurelia AGA possessed an N-terminal signal peptide and potential N-glycosylation sites. The genomic region of Aurelia AGA was approximately 9.8 kb in length and contained 12 exons and 11 introns. Quantitative RT-PCR analysis revealed that AGA expression increased during strobilation, and was then decreased in medusae. To inhibit AGA function, we administered the lysosomal acidification inhibitors, chloroquine or bafilomycin A1, to animals during strobilation. Both inhibitors disturbed medusa morphogenesis at the oral end, suggesting involvement of lysosomal hydrolases in strobilation.

Alisol B, a triterpene from Alismatis rhizoma (dried rhizome of Alisma orientale), inhibits melanin production in murine B16 melanoma cells.

To develop new whitening agents from natural products, we screened 80 compounds derived from crude drugs in Kampo medicine in a melanin synthesis inhibition assay using murine B16 melanoma cells. The screen revealed that treatment with alisol B, a triterpene from Alismatis rhizoma, significantly decreased both melanin content and cellular tyrosinase activity in B16 cells. However, alisol B did not directly inhibit mushroom tyrosinase activity in vitro. Therefore, we investigated the mechanism underlying the inhibitory effect of alisol B on melanogenesis. Alisol B suppressed mRNA induction of tyrosinase and its transcription factor, microphthalmia-associated transcription factor (MITF). Furthermore, alisol B reduced the phosphorylation of CREB and maintained the activation of ERK1/2. These results suggest that the reduction in melanin production by alisol B is due to the downregulation of MITF through the suppression of CREB and activation of ERK and that alisol B may be useful as a new whitening agent.

Dietary supplemental vitamin B6 increases carnosine and anserine concentrations in the heart of rats.

This study was performed to examine the effect of dietary level of vitamin B6 on the concentrations of carnosine and anserine, antioxidants, in the heart of rats. Analysis using UPLC-MS/MS showed that the concentrations of these dipeptides in the 7 and 35 mg pyridoxine HCl/kg groups were significantly higher than those in the 1 mg pyridoxine HCl/kg group, implying the novel role of dietary vitamin B6 as a determinant of the dipeptides favorable for heart.

RASSF6 expression in adipocytes is down-regulated by interaction with macrophages.

Macrophage infiltration into adipose tissue is associated with obesity and the crosstalk between adipocytes and infiltrated macrophages has been investigated as an important pathological phenomenon during adipose tissue inflammation. Here, we sought to identify adipocyte mRNAs that are regulated by interaction with infiltrated macrophages in vivo. An anti-inflammatory vitamin, vitamin B6, suppressed macrophage infiltration into white adipose tissue and altered mRNA expression. We identified >3500 genes whose expression is significantly altered during the development of obesity in db/db mice, and compared them to the adipose tissue mRNA expression profile of mice supplemented with vitamin B6. We identified PTX3 and MMP3 as candidate genes regulated by macrophage infiltration. PTX3 and MMP3 mRNA expression in 3T3-L1 adipocytes was up-regulated by activated RAW264.7 cells and these mRNA levels were positively correlated with macrophage number in adipose tissue in vivo. Next, we screened adipose genes down-regulated by the interaction with macrophages, and isolated RASSF6 (Ras association domain family 6). RASSF6 mRNA in adipocytes was decreased by culture medium conditioned by activated RAW264.7 cells, and RASSF6 mRNA level was negatively correlated with macrophage number in adipose tissue, suggesting that adipocyte RASSF6 mRNA expression is down-regulated by infiltrated macrophages in vivo. Finally, this study also showed that decreased RASSF6 expression up-regulates mRNA expression of several genes, such as CD44 and high mobility group protein HMGA2. These data provide novel insights into the biological significance of interactions between adipocytes and macrophages in adipose tissue during the development of obesity.

Regulation of colon gene expression by vitamin B6 supplementation.

SCOPE: Previous studies have shown that vitamin B6 supplementation suppresses the development of colonic aberrant crypt foci (ACF), precursor lesions of colon cancer, and cell proliferation in mice receiving the colonic carcinogen, azoxymethane (AOM). This study investigated the molecular mechanism of these effects of dietary vitamin B6. METHODS AND RESULTS: To date, the mechanism by which ACFs develop is not yet fully understood. In a search for factors that play a critical role during ACF development, we examined colon gene expression during early stage of ACF development in AOM-treated mice using DNA microarray analysis. AOM treatment significantly upregulated mRNA closely related to mast cell and cytotoxic T-cell activity. This study also investigated the effect of vitamin B6 supplementation on colon gene expression in AOM-treated mice. We found that vitamin B6 supplementation downregulates Cd8a and Ccl8 mRNA expression, suggesting these candidate genes may play a protective role against colonic ACF development. Furthermore, we examined genomic affects of dietary vitamin B6, and showed that Reg3γ mRNA expression in colons is downregulated by vitamin B6. CONCLUSION: This study provides an insight into the genomic activities of dietary vitamin B6 that may be protective against colon tumor development.

Consumption of vitamin B(6) reduces fecal ratio of lithocholic acid to deoxycholic acid, a risk factor for colon cancer, in rats fed a high-fat diet.

To examine the effect of supplemental dietary vitamin B(6) on the colonic luminal environment, growing male rats were fed a high-fat diet containing 1, 7, or 35 mg pyridoxine HCl/kg diet for 6 wk. Food intake and growth were unaffected by the dietary treatment. Supplemental dietary vitamin B(6) significantly reduced the production of a fecal secondary bile acid, lithocholic acid (the most toxic secondary bile acid and a risk factor for colon cancer), and markedly reduced the ratio of lithocholic acid to deoxycholic acid (a less toxic secondary bile acid) in feces (p<0.05). Increasing dietary vitamin B(6) increased fecal mucin levels (a marker of intestinal barrier function) in a dose-dependent manner (p<0.05) but did not affect fecal immunoglobulin A levels (an index of intestinal immune function). Cecal levels of organic acids were not significantly affected by supplemental dietary vitamin B(6). These results suggest the possibility that dietary vitamin B(6) affects the colonic luminal environment by altering the production of secondary bile acids and mucins.

Comparative study on the responses of concentrations of B6-vitamers in several tissues of mice to the dietary level of pyridoxine.

To examine the responses of the levels of B6-vitamers in several tissues to the dietary level of pyridoxine (PN), mice were fed diets containing 0, 1, 7 (the recommended level) or 35 mg PN HCl/kg diet for 5 wk. Compared with the 0 mg PN HCl/kg diet, the 35 mg PN HCl/kg diet caused the highest elevation in the concentration of pyridoxal 5'-phosphate (PLP) in small intestine and epididymal adipose tissue, moderate elevation in colon, lung, spleen and stomach, slight elevation in brain, kidney and liver (p<0.05), and no elevation in heart and gastrocnemius muscle. In general, the alterations in PLP level in many tissues and serum were remarkable for diets between 1 mg and 7 mg PN HCl/kg diets. Compared to the 7 mg PN HCl/kg diet, the 35 mg PN HCl/kg diet further elevated the PLP level in adipose tissue, spleen and stomach (p<0.05). Dietary supplemental PN elevated the level of PN in small intestine and colon in a dose-dependent manner (p<0.05), but not in other tissues. There was a significant correlation between the PN and PLP levels in small intestine and colon (p<0.05), implying that PN absorbed from the diet can be at least in part metabolized to PLP within the absorptive intestinal cells. The results suggest that the responses of concentrations of B6-vitamers to dietary level of PN greatly differ among several tissues.

Vitamin B6 suppresses serine protease inhibitor 3 expression in the colon of rats and in TNF-α-stimulated HT-29 cells.

SCOPE: Previous reports in the areas of animal studies and, recently epidemiology, have linked anti-tumorigenic and anti-inflammatory effects to dietary vitamin B6. This study investigated the molecular mechanism of these effects of vitamin B6. METHODS AND RESULTS: DNA microarray analysis was used to obtain information on changes in colon gene expression from vitamin B6 (pyridoxine) repletion in vitamin B6-deficient rats. Pyridoxine supplementation down-regulated the inflammatory molecule, serine protease inhibitor clade A member 3 (SPI-3) mRNA expression in the colon. This study also showed that tumor necrosis factor α (TNF-α) induced SPI-3 mRNA expression in HT-29 human colon cancer cells, and vitamin B6 (pyridoxal hydrochloride) pretreatment of HT-29 cells inhibited TNF -induced mRNA expression of SPI-3. Vitamin B6 inhibited TNF-α-induced NF-κB activation via suppression of IκBα degradation in HT-29 cells. HT-29 cells stably expressing epitope-tagged ubiquitin were generated and vitamin B6 pretreatment was shown to inhibit ubiquitination of the IkB protein in response to TNF-α-i. CONCLUSION: Vitamin B6 suppressed SPI-3 expression in the colon of rats and in TNF-α-stimulated HT-29 cells. Further, this study showed a possible role of vitamin B6 in the regulation of protein ubiquitination.

Consumption of vitamin B6 reduces colonic damage and protein expression of HSP70 and HO-1, the anti-tumor targets, in rats exposed to 1,2-dimethylhydrazine.

Mounting evidence indicates that vitamin B6 is a protective factor for colon cancer. Elevations in colonic damage, cell proliferation and heat shock proteins (HSPs, molecular chaperones) have been suggested to be associated with colon carcinogenesis. This study was performed to examine the effect of dietary levels of vitamin B6 (1, 7 or 35 mg pyridoxine HCl/kg diet) for 22 weeks on colon damage, epithelial cell proliferation and expression of HSPs in rats exposed to 1,2-dimethylhydrazine (DMH). Supplemental vitamin B6 with a low vitamin B6 diet (1 mg pyridoxine HCl/kg diet) significantly reduced fecal activity of intestinal alkaline phosphatase (an index of intestinal damage) and the colonic epithelium PCNA labeling index (a marker of cell proliferation). Analysis using ELISA indicated that supplemental vitamin B6 significantly lowered protein levels of colonic HSP70 and heme oxygenase-1, HSP32 (HO-1). However, real-time RT-PCR analysis revealed that the mRNA levels of these HSPs were not decreased by supplemental vitamin B6, suggesting that the lowering effect of vitamin B6 on the colon protein expression of the HSPs is mediated by mechanisms not involving altered gene expression. This study provided evidence that dietary supplemental vitamin B6 suppresses colon damage, epithelial cell proliferation and protein expression of HSP70 and HO-1, the targets for anti-tumor agents, in rats exposed to DMH.

Identification and physiological evaluation of the components from citrus fruits as potential drugs for anti-corpulence and anticancer.

On the basis of monitoring the prevention of accumulation of lipid droplets in mouse 3T3-L1 preadipocyte cells and inhibition of the proliferation of human colon cancer HT-29 cells, effective anti-corpulence and anticancer compounds were isolated from the peel of Citrus fruits. These bioactive components were identified as polymethoxyflavones and coumarin derivatives by spectroscopic analyses. 5-Hydroxy-6,7,8,3',4'-pentamethoxyflavone had the greatest anti-corpulence effects and 3,5,6,7,8,3',5'-heptamethoxyflavone had the greatest anticancer effects. Furthermore, distributions of those bioactive components in the peel of 10 species of Citrus fruits were demonstrated by HPLC analyses.

High protein buckwheat flour suppresses hypercholesterolemia in rats and gallstone formation in mice by hypercholesterolemic diet and body fat in rats because of its low protein digestibility.

OBJECTIVE: This study evaluated the physiologic properties of high protein buckwheat flour (PBF) by examining its effects on serum cholesterol and body fat in rats and on cholesterol gallstone formation in mice. METHODS: Animals were fed experimental diets that contained casein, buckwheat protein extract (BWP), or PBF as a protein source (net protein content 200 g/kg). RESULTS: In experiment 1, consumption of PBF and BWP for 10 d caused 33% and 31% decreases, respectively, in serum cholesterol of rats fed cholesterol-enriched diets when compared with consumption of casein (P < 0.05). Dietary PBF caused a significant decrease in liver cholesterol, whereas dietary BWP caused only a slight decrease (P > 0.05). Fecal excretion of neutral and acidic steroids in the PBF group was significantly higher than those in the BWP and casein groups. In experiment 2, consumption of PBF for 10 d significantly suppressed adipose tissue weight and hepatic activity of fatty acid synthase in rats fed cholesterol-free diets compared with consumption of casein (P < 0.05), whereas that of BWP for this period caused only a slight decrease in adipose tissue weight (P > 0.05). In experiment 3, dietary PBF and BWP significantly decreased the incidence of cholesterol gallstones and lithogenic index in mice fed cholesterol-enriched diets for 27 d, which was associated with increased fecal excretion of acidic steroids. CONCLUSION: This study demonstrated that PBF has strong activities against hypercholesterolemia, obesity, and gallstone formation, suggesting a potential usefulness of PBF as functional ingredient.

A high-fat diet enhances the inhibitory effect of dietary vitamin B6 on colon cell proliferation in mice.

Previously we reported that dietary supplemental vitamin B6 (B6) reduced colon tumorigenesis and cell proliferation in mice receiving azoxymethane (AOM) for 22 weeks. This study was conducted to examine the influence of short-term consumption (5 weeks) of diets containing graded levels of B6 and fat on colonic cell proliferation in mice with or without receiving AOM. In experiment 1, mice were fed the 10% corn oil diet containing 1, 7, 14, 35 or 70 mg pyridoxine HCl/kg, and received weekly injections of AOM for the initial 3 weeks. In experiment 2, mice were fed 5 or 20% corn oil diet containing 1, 7, 14 or 35 mg pyridoxine HCl/kg, and received weekly injections of AOM or saline for the initial 3 weeks. In experiment 1, supplemental B6 caused a dose-dependent reduction of colon aberrant crypt foci and cell proliferation (BrdU-labeling index) among the 1-14 mg pyridoxine HCl/kg. There was no influence of B6 on these parameters among 14-70 mg pyridoxine HCl/kg. Immunohistochemical analysis of apoptosis labeling by TUNEL method indicated no influence of dietary B6 on colon apoptosis. In experiment 2, supplemental B6 significantly reduced colon cell proliferation regardless of AOM injection. This inhibitory effect on cell proliferation was markedly enhanced by a high-fat diet, but slightly affected by AOM treatment. The results suggest that dietary supplemental B6 inhibits colon cell proliferation from the early stage of colon carcinogenesis, and a high-fat diet markedly enhances the inhibitory effect.

Short-term feeding of fish oil down-regulates the expression of pyruvate dehydrogenase E1 alpha subunit mRNA in mouse brain.

Previous studies have suggested that docosahexaenoic acid (DHA), contained in fish oil, prevents brain disease. In the current study, the effect of fish oil feeding on gene expression in the brain was investigated by suppression subtractive hybridization. We found that pyruvate dehydrogenase E1 alpha (PDHE1alpha) mRNA expression is down-regulated by fish oil feeding. We examined whether the expression of PDHE1alpha mRNA is altered by DHA treatment in differentiated PC12 cells. PDHE1alpha mRNA was reduced by supplementation of DHA with a significant decrease in cellular ATP level. These results indicate that fish oil feeding might modulate energy metabolism in the brain.