Diaminopimelic Acid Synthesis in Cultures of an Escherichia coli Double Auxotroph: Effects of Cultural Conditions

The metabolic response to L-lysine of Escherichia coli ATCC 13002, a lysine-histidine double auxotroph, has been examined in a synthetic medium containing sucrose. In shaken cultures largest amounts of extracellular DAP were produced with an initial lysine concentration of 7·5 mg/1 and in static cultures of 2·5 mg/1. Considerably smaller amounts of DAP accumulated under stationary conditions. In cultures shaken for 20 and 43 h there was an overall decrease in the yields of DAP, expressed in terms of cell biomass and of sucrose consumed, as the initial concentration of lysine was increased from 0·75 mg/1 in steps up to 25 mg/1. The regulatory effect of lysine on DAP production was also observed when lysine was supplied to cultures at a constant rate employing diffusion capsules.     

Higher level of plasma bioactive molecule sphingosine 1-phosphate in women is associated with estrogen

Both sphingosine 1-phosphate (S1P) and estrogen have been documented to play endothelial protective roles. However, it remains unclear whether estrogen could regulate the anabolism of the bioactive molecule S1P and the underlying mechanisms. In this study, 108 healthy participants were separated into three age groups, and their plasma S1P levels were analyzed by liquid chromatography tandem mass spectrometry. Results showed that the plasma S1P levels were significantly higher in women than those in men within the age of 16–55 years old and higher in pre-menopausal than post-menopausal women. The experiment in C57 BL/6 mice confirmed the gender difference of plasma S1P level. In vitro study demonstrated that after the stimulation of 17β-estradiol (E2), S1P levels both in EA.hy926 cells and the culture media were increased about 9 and 3 times, respectively; the mRNA expression, the protein level and the activity of sphingosine kinase (SphK) 1, not SphK2, were markedly increased; the mRNA and protein expression of ATP-binding cassette transporter (ABC) C1, G2 and S1P transporter spinster homolog 2 (Spns2) were significantly elevated; furthermore, the mRNA and protein expressions of S1P receptors (S1PRs) 1–2 were increased in a time-dependent manner. This study suggests that E2 markedly improves S1P synthesis by activating SphK1 and induces S1P export via activating ABCC1, G2 and Spns2 from endothelium system, which may consequently lead to the gender difference of plasma S1P in adult human and mouse. The results of this study suggest that E2 may exert its vasculoprotective function by activation of the SphK1–S1P–S1PR signaling axis.     

Aerobic training increases the expression of adiponectin receptor genes in the peripheral blood mononuclear cells of young men

Little is known about the effect of exercise training on the expression of adiponectin receptor genes in peripheral blood mononuclear cells (PBMCs). In this study, we investigated the effects of aerobic training on the expression of AdipoR1 and AidpoR2 mRNAs in PBMCs, whole body insulin sensitivity, and circulating adiponectins in men. Thirty young men were randomly assigned to either a control (n=15) or an exercise (n=15) group. Subjects assigned to the exercise group underwent a 12-week jogging and/or running programme on a motor-driven treadmill at an intensity of 60%-75% of the age-based maximum heart rate with duration of 40 minutes per session and a frequency of 5 days per week. Two-way mixed ANOVA with repeated measures was used to test any significant time-by-group interaction effects for the measured variables at p=0.05. We found significant time-by-group interaction effects for waist circumference (p=0.001), VO_2max (p<0.001), fasting insulin (p=0.016), homeostasis model assessment for insulin resistance (HOMA-IR) (p=0.010), area under the curve (AUC) for insulin response during the 75-g oral glucose tolerance test (p=0.002), high-molecular weight (HMW) adiponectin (p=0.016), and the PBMC mRNA levels of AdipoR1 (p<0.001) and AdipoR2 (p=0.001). The exercise group had significantly increased mRNA levels of AdipoR1 and AdipoR2 in PBMCs, along with increased whole body insulin sensitivity and HMW adiponectin, decreased waist circumference, and increased VO_2max compared with the control group. In summary, the current findings suggest that exercise training modulates the expression of AdipoR1 and AdipoR2 mRNAs in PBMCs, implying that manipulation of the expression of these genes could be a potential surrogate for lifestyle intervention-mediated improvements of whole body insulin sensitivity and glucose homeostasis.