Activation of brain lactate receptor GPR81 aggravates exercise-induced central fatigue.

Exercise-induced fatigue is a complex physiological phenomenon and is greatly influenced by central mechanisms in brain. As one of the most abundant circulating carbon metabolites, l-lactate in brain has been considered to be an important supplementary fuel during exercise; however, whether it plays a signaling role in fatigue remains largely obscure. In this study, our results initially revealed that brain l-lactate levels were increased after an exhaustive swimming session in several brain regions including motor cortex, hippocampus, and cerebellum. Then, we examined the specific role of brain lactate receptor, also known as hydroxycarboxylic acid receptor 1 (GPR81), in exercise-induced fatigue. We found that intracerebroventricular injection of either d-lactate (an enantiomer that could mediate activation of GPR81 as l-lactate) or a potent GPR81 agonist 3-chloro-5-hydroxybenzoic acid (CHBA), significantly decreased the swimming time to fatigue. After being subjected to the same weight-loaded swimming for 30 min, no obvious changes of blood lactate levels, gastrocnemius pAMPK/AMPK ratio, and glycogen contents were observed between intracerebroventricular CHBA-injected mice and vehicle-treated ones, which suggested a comparable degree of peripheral fatigue. Meanwhile, there were higher extracellular γ-aminobutyric acid (GABA) levels and lower extracellular glutamate levels and glutamate/GABA ratio in motor cortex of the intracerebroventricular CHBA-injected mice than that of vehicle-treated ones, indicating a greater extent of central fatigue in CHBA-injected mice than that in vehicle animals. Collectively, our results suggested that an increased level of brain l-lactate acts as a signaling molecule via activating GPR81, which in turn exacerbates central fatigue during exercise.

Rapid determination of capsaicin concentration in soybean oil by terahertz spectroscopy.

Capsaicin is the key composition of pepper and can be used as a marker of gutter oil for detection. The feasibility of rapid detection of capsaicin concentration in soybean oil was studied by terahertz spectroscopy. Genetic algorithm (GA) and principal component analysis (PCA) as the pretreatment method were used to obtain the best spectral features. Least square-support vector machine (LS-SVM), back propagation neural network (BPNN), and partial least squares (PLS) were combined with the pretreatment method to obtain the best determination model. The BPNN was combined with GA to obtain the best quantitative prediction results with the correlation coefficient of prediction (RP ), prediction root mean square error (RMSEP), the ratio of prediction to deviation (RPD), and range error ratio (RER) were 0.9309, 0.4030 µg/kg, 17.0421, and 2.4813, respectively. Furthermore, the detection limit of capsaicin could achieve 1.25 µg/kg in soybean oil and the accuracy of discrimination was up to 100% in the prediction set using the LS-SVM combined with GA pre-treatment. The results suggested that terahertz spectroscopy together with chemometric methods would be a promising technique for rapid determination of capsaicin concentration in soybean oil. Meanwhile, it is necessary to perform further experiments with real gutter oil samples before applying the method in practice. PRACTICAL APPLICATION: The combination of terahertz spectroscopy technology and chemometrics is a promising method for the rapid determination of capsaicin concentration in soybean oil with high efficiency.

Optimization of selenoprotein P and other plasma selenium biomarkers for the assessment of the selenium nutritional requirement: a placebo-controlled, double-blind study of selenomethionine supplementation in selenium-deficient Chinese subjects.

BACKGROUND: The intake of selenium needed for optimal health has not been established. Selenoproteins perform the functions of selenium, and the selenium intake needed for their full expression is not known. OBJECTIVE: This study sought to determine the intake of selenium required to optimize plasma selenoprotein P (SEPP1) and to compare SEPP1 with other plasma selenium biomarkers. DESIGN: A 40-wk placebo-controlled, double-blind study of selenium repletion was carried out in 98 healthy Chinese subjects who had a daily dietary selenium intake of 14 micro g. Fourteen subjects each were assigned randomly to daily dose groups of 0, 21, 35, 55, 79, 102, and 125 micro g Se as l-selenomethionine. Plasma glutathione peroxidase (GPX) activity, SEPP1, and selenium were measured. A biomarker was considered to be optimized when its value was not different from the mean value of the subjects receiving larger supplements. RESULTS: The SEPP1 concentration was optimized at 40 wk by the 35- micro g supplement, which indicated that 49 micro g/d could optimize it. GPX activity was optimized by 21 micro g (total ingestion: 35 micro g/d). The selenium concentration showed no tendency to become optimized. CONCLUSIONS: The present results indicate that SEPP1 concentration is the best plasma biomarker studied for assessing optimal expression of all selenoproteins, because its optimization required a larger intake of selenium than did GPX activity. On the basis of the selenium intake needed for SEPP1 optimization with adjustments for body weight and individual variation, ap 75 micro g Se/d as selenomethionine is postulated to allow full expression of selenoproteins in US residents. This trial was registered at clinicaltrials.gov as NCT00428649.

[Effect of zinc on thymulin level in mice].

OBJECTIVE: In order to investigate the roles of the different levels of zinc nutrition status on the thymulin of the mice. METHODS: The experiment included two periods: zinc depleted period and repletion period. In the depleted period, mice were divided into 3 dose groups: zinc deficient group (ZD, 5.2 mg/kg), zinc pair-fed group (PZ) and normal zinc group(NZ,25.6 mg/kg). In the repletion period, mice were divided into 3 dose groups: ZD group, DZ-NZ group and PZ-NZ group. RESULTS: The results showed that a signification decrease of thymulin level was observed as a result of zinc deficiency and was increased rapidly follow zinc supplement, while the plasma zinc was kept the same level. CONCLUSION: The thymulin is a sensitive biomarker for assess the zinc status.

Effectiveness of selenium supplements in a low-selenium area of China.

BACKGROUND: Selenium is an essential micronutrient with a recommended dietary allowance for adults of 55 mug/d. It functions as an essential constituent of selenoproteins. Although there is no evidence of selenium deficiency in the United States, people in many other areas of the world are selenium deficient, with the consequence that they are unable to express their selenoproteins fully. OBJECTIVE: We carried out a supplementation trial in a selenium-deficient population in China to assess the requirement for selenium as selenite and as selenomethionine. DESIGN: One hundred twenty subjects with an average selenium intake of 10 mug/d were randomly assigned and administered tablets containing no selenium or amounts as high as 66 mug Se/d for 20 wk. Plasma was sampled before supplementation and at 4-wk intervals during supplementation and was assayed for the 2 plasma selenoproteins, glutathione peroxidase and selenoprotein P. RESULTS: Full expression of glutathione peroxidase was achieved with 37 mug Se/d as selenomethionine and with 66 mug/d as selenite. Full expression of selenoprotein P was not achieved at the highest doses of either form. CONCLUSIONS: Full expression of selenoprotein P requires a greater selenium intake than does full expression of plasma glutathione peroxidase. This suggests that selenoprotein P is a better indicator of selenium nutritional status than is glutathione peroxidase and that the recommended dietary allowance of selenium, which was set with the use of glutathione peroxidase as the index of selenium status, should be revised. Selenium as selenomethionine had nearly twice the bioavailability of selenium as selenite.

[Effect of zinc on immune function in mice spleen lymphocytes].

OBJECTIVE: In order to study the effects of different levels of zinc nutrition status on the immune function of mice spleen lymphocytes. METHODS: The experiment included two periods: zinc depleted period and repletion period. In the depleted period, mice were divided into 3 dose groups: zinc deficient group (ZD, 5.2mg/kg), zinc pair-fed group (PZ) and normal zinc group (NZ, 25.6 mg/kg). In the repletion period, mice were divided into 3 dose groups: ZD group, DZ-NZ group and PZ-NZ group. It was measured some biomarkers of immunity to assess the zinc nutritional status, including lymphocytes amount, lymphocytes proliferation index and IL-2 activity. RESULTS: The lymphocytes counts of ZD group spleen showed significant decline at seventy days fed zinc deficiency diets. The counts of ZD-NZ group were increased after 22 days of taking normal zinc diet. Zinc deficiency could suppressed the proliferation of the spleen lymphocytes. The spleen lymphocytes proliferation of the ZD-NZ group showed a moderate but non-significant increase compared with the ZD group. Zinc deficiency could decrease IL-2 production. The production of IL-2 of ZD group was lower than those of ZP (P < 0.05), IL-2 production increased following zinc supplement. CONCLUSION: It is found that zinc status can affect the immune function. Production of IL-2 in spleen lymphocyte is affected evidently by zinc.

[Coxsackievirus B3 infection and Keshan disease].

To study the relationship between the infection of enteroviruses and the etiology of keshan disease, we examined the 30 blood samples from the latent-chronic KD patients from Mianning, Xider, Derchang county of Sichuan Province with LDE-PCR (long distance enterovirus-specific RT PCR), two sensitive and specific ELISAs (one for CVB1-6 IgM and the other for CVB1-6 IgG), and three-primer RT PCR specific for CVB3. Results show that: 1) The infection rate of enteroviruses in the samples from the latent-chronic KD patients is higher than from the control group (80% VS 0%, P < 0.01); 2) The CVB1-6 antibody positive rate in latent-chronic KD is higher than that of the control group (IgM, 33% VS 0%, P < 0.01; IgG, 23% VS 0%, P < 0.01); 3) 16.6% (4/24) of enteroviruses positive samples or 40% (4/10) of CVB1-6 IgM antibody positive samples can be identified as CVB3. So, the infection of enter viruses maybe involves in the cause and development of latent-chronic keshan disease, and at least we conclude that the mutation of CVB3 is not the only cause of KD.