Effect of GABA on oxidative stress in the skeletal muscles and plasma free amino acids in mice fed high-fat diet.

Increased levels of plasma free amino acids (pFAAs) can disturb the blood glucose levels in patients with obesity, diabetes mellitus and metabolic syndrome (MS) and are associated with enhanced protein oxidation. Oxidation of proteins, especially in the muscles, can promote protein degradation and elevate the levels of pFAAs. Gamma-aminobutyric acid (GABA), a food additive, can reduce high-fat diet (HFD)-induced hyperglycaemia; however, the mechanisms remain unclear. The aim of this study was to evaluate the effects of GABA on protein oxidation and pFAAs changes. One hundred male C57BL/6 mice were randomly divided into five groups that were fed with control diet, HFD and HFD supplied with 0.2%, 0.12% and 0.06% GABA in drinking water for 20 weeks respectively. HFD feeding led to muscular oxidative stress, protein oxidation, pFAA disorders, hyperglycaemia and augmented plasma GABA levels. Treatment with GABA restored normally fasting blood glucose level and dose-dependently inhibited body weight gains, muscular oxidation and protein degradation. While medium and low doses of GABA mitigated HFD-induced pFAA disorders, the high dose of GABA deteriorated the pFAA disorders. Medium dose of GABA increased the levels of GABA, but high dose of GABA reduced the levels of plasma GABA and increased the activity of succinic semialdehyde dehydrogenase in the liver. Therefore, treatment with GABA mitigated HFD-induced hyperglycaemia probably by repairing HFD-induced muscular oxidative stress and pFAA disorders in mice. Our data also suggest that an optimal dose of GABA is crucial for the prevention of excess GABA-related decrease in the levels of pFAA and GABA as well as obesity.

Lactobacilli prevent hydroxy radical production and inhibit Escherichia coli and Enterococcus growth in system mimicking colon fermentation.

AIMS: To explore the effect of Lactobacillus on redox state of colon chyme. METHODS AND RESULTS: Nine Lactobacillus strains were studied for the inhibition of lipid peroxide formation in Fe(2+)/ascorbate system and for their ability to chelate 'free' ferrous ion. The result shows both properties were strain specific and no relationship between them was found. Both properties of Lactobacillus paracasei Fn032, Lactobacillus rhamnosus GG (LGG) and Lactobacillus sp. Fn001 were successively decreasing. LGG and Fn032 significantly decreased hydroxyl radicals (P < 0.01) in colonic fermentation model, in which considerable hydroxyl radicals occurred spontaneously. Addition of ferrous ion induced the production of hydroxyl radicals, which could be significantly inhibited by LGG, Fn032 (P < 0.01) and Fn001 (P < 0.05). Ferrous ion significantly induced the growth of Enterococcus and Escherichia coli, which could be inhibited by all three Lactobacillus strains. Escherichia coli and Enterococcus show significantly positive correlation with hydroxyl radicals with R of 0.96 (P = 0.0002) and 0.91 (P = 0.0017), respectively. CONCLUSIONS: Antioxidative Lactobacillus could modulate redox state in colonic fermentation system, which is related to their free radical-scavenging ability or antibacterial effect. SIGNIFICANCE AND IMPACT OF THE STUDY: This study proves that Lactobacillus strain could influence the redox state of gut chyme. Evaluation of antioxidative ability might be a powerful method for screening probiotic Lactobacillus strains.

Dietary nucleotides protect thymocyte DNA from damage induced by cyclophosphamide in mice.

The effects of dietary nucleotides on thymocyte DNA damages induced by cyclophosphamide (CP) in mice were examined. First, phase I experiment was conducted to determine the optimal timing of detecting thymocyte DNA damages induced by CP (150 mg/kg body weight) in mice. Thymocyte DNA damages was determined at 6, 12, 18, 24 h by single-cell gel electrophosphoresis assay (comet assay) after intraperitoneal injection of CP. The levels of DNA damage at 6, 12, 18, 24 h were all significantly higher than that of the control group (p < 0.01). The highest level of DNA damage appeared at 18 h and then decreased at 24 h. Therefore, 18 h was selected to determine DNA damages induced by CP in subsequent experiments. In phase II experiment, 30 male KunMing mice were divided into three treatments: negative control (NC), positive control (PC) and nucleotides group (NG). Mice in NC and PC were fed nucleotide-free diet, and mice in NG were fed nucleotide-supplemented diet (supplemented with 0.25% nucleotides, a mixture containing equal amounts of AMP, CMP, GMP and UMP). Mice in PC and NG groups were injected with CP (150 mg/kg body weight) at 21 days. DNA damage in thymocytes was evaluated at 18 h after CP treatment. The results indicate that dietary nucleotides do not affect the weights of the thymus and the spleen, or their organ indices (p > 0.05), but significantly decrease the percentage of comet cells and comet tail sizes (p < 0.01). This study demonstrates that dietary nucleotides could reduce the level of thymocyte DNA damage induced by CP in mice.

Factors involved in binding of Lactobacillus plantarum Lp6 to rat small intestinal mucus.

AIM: To investigate the adhesion determinants of Lactobacillus plantarum Lp6, a dairy isolate. METHODS AND RESULTS: Small intestinal mucus extracted from rats was used as a substrate for adhesion. Adhesion determinants were studied by physical, chemical and enzymatic pretreatments of the bacteria, and adhesion inhibition assay. The mannose-specific adhesins were explored by studying the effect of d-mannose on adhesion and the yeast-agglutinating ability of the bacteria. It was found that adhesion decreased after bacteria were treated with sodium metaperiodate, protease K, trypsin, lithium chloride and trichloroacetic acid. However, adhesion did not decrease after trypsin-treated bacteria were incubated with cell surface protein extract. Cell surface bound exopolysaccharides were found to inhibit the adhesion. D-mannose inhibited the adhesion in a dose-dependent manner. The bacteria could significantly agglutinate yeast and lost this ability after protease K treatment. CONCLUSIONS: Adhesion was mainly mediated by the mannose specific adhesins, which might be proteins that reversibly bind to the cell surface components. Cell surface-bound exopolysaccharides were also involved in adhesion. SIGNIFICANCE AND IMPACT OF THE STUDY: The mannose-specific adhesion of Lact. plantarum Lp6 to rat mucus might be important for competing with pathogens-binding sites in gut, which may be used to resist the colonization of the pathogens.

[Effects of nutrition condition on pcDNA3-HBS plasmid DNA production].

To investigate the effects of nutrition condition on plasmid DNA production, Escherichia coli JM109 containing plasmid pcDNA3S-HBA was grown in different culture media. Results show that carbon source, nitrogen source affected plasmid DNA yield significantly. Glucose and peptone was selected, since they were preferable to other investigated carbon source and nitrogen source. In M9P medium, the appropriate concentration of(NH4)2SO4 was important for plasmid DNA production, Gly, Asp, Gln were formulated into the M9G medium because they served as the nitrogen donors for nucleotides synthesis. With addition of 1.2 g/L Asp, 1.0 g/L Gln and 0.4 g/L Gly into M9G medium, plasmid DNA yield was 25 mg/L after 20 h culture. Foreign nucleotides distinctively affected plasmid DNA production. With addition of 0.4 g/L nucleosides mixture of thymidine and cytidine(moles fraction of thymidine:cytidine = 1:1) into M9P medium, plasmid DNA yield was 35 mg/L.