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Objective: To determine protein requirement of Chinese young female adults on habitual Chinese diet through indicator amino acid oxidation (IAAO) technique.Design: Twenty women with a mean (SD) age of 21.6 (0.9) years were healthy based on questionnaire, physical examinations and screening tests. There were three consecutive periods of 7 days each with six different intakes of protein (0.70, 0.78, 0.86, 0.94, 1.02 and 1.10 g/kg·d) within Chinese habitual diets (proportions of good-quality protein were 40 to 45%). Subjects were randomly allocated equally into two groups (1.10, 0.86, 0.78 g/kg·d for group 1 and 1.02, 0.94, 0.70 g/kg·d for group 2 from period 1 to period 3 in turn). Adaptation days were from day 1 to day 6 and the isotope study day was day 7 in each period. Amino acid kinetics was measured in non-menstrual periods, based on the IAAO technique. Two indicators (rate of release of 13CO2 and rate of leucine oxidation) were used to estimate protein requirement by breakpoint analysis with a two-phase linear regression crossover model.Results: Mean and population safe protein requirements of Chinese habitual diets in non-menstrual periods from the rate of release of 13CO2 were 0.91 and 1.09 g/kg·d, respectively. And from the rate of leucine oxidation were 0.92 and 1.10 g/kg·d, respectively.Conclusions: The protein requirement of young women on Chinese habitual diets in non-menstrual period was lower than the current protein reference intake for Chinese females. Further studies are necessary to explore female protein requirements during the whole menstrual cycle. [ABSTRACT FROM AUTHOR]

Objective: To assess the validity and reliability of the infrared spectrometry for measuring the delta over baseline for breath 13C., Method: Twenty-four healthy adults were selected, including twelve males and twelve females. 13C-Leucine was used as tracer in stable isotope metabolic experiments. One baseline breath was collected before the tracer protocol began. Other breath samples were collected at 60, 120, 180, 195, 210, 225, 240, 255, 270 and 300 min post-tracer challenge. The delta over baseline for breath 13C was measured by the infrared spectrometry and Heliview 13C breath analyzer., Results: No significant differences were found between the infrared spectrometry and Heliview 13C breath analyzer in measuring the delta over baseline for breath 13C. The F value and p value of two-way ANOVA were 0.29 and 0.5874 respectively. The t and p value of consistency test were 0.48 and 0.6346 respectively., Conclusion: The 13C infrared spectrometry can reliably measure the delta over baseline for breath 13C.

Objective: To analyze the end product enrichment of the stable isotope labeled amino acid in different time points and the level of catabolism of different protein dose groups under the infusion state of the labeled amino acid in the study of amino acid metabolic kinetics, supplying the data support for the the setting of sampling time in the study of the physiological requirement of protein and amino acid., Method: Twenty subjects were divided into two groups and were supplied two different doses of protein, all subjects were administered the 13C-leucine for 3 hours by the left basilic vein at 12:00 on day 6 and respired air samples were collected per 15 minutes during the last 30 minutes of infusion, analyzing the 13C enrichment difference at three time points and the 13CO2 production rate of the two dietary protein dose groups to determine whether 13C enrichment was stable or not and how the dietary protein dose influence the 13CO2 production rate., Result: The difference of 13C enrichment is not significant at three time points for every group subjects (P > 0.05), the 13CO2 production rate of the protein dose group of 0.89 g/kg/d was significantly higher than that of the protein dose group of 0.89 g/kg/d (P < 0.05)., Conclusion: It was suggested that determine one specific time point were determined to compare the metabolic kinetics changes of the different protein and amino acid dose groups, when the physiological requirement of protein and amino acid was explored, and the catabolism level in the bigger dose group was higher than that in the smaller dose group.

Objective: To explore the expired air plateau period by oral administration of 13C-Leucine during feeding state in study of amino acid metabolism kinetics., Methods: Six healthy adult women were selected as subjects, 13C-leucine was orally administrated for 4 hours during feeding state on day 6 after 5 days of adaptation period. The expired air was collected during the course of administration and 1 hour after the end of administration to determine the delta over baseline for 13C., Results: The delta over baseline for 13C in expired air was steady at a higher level during period of half hour before and after the end of administration respectively., Conclusion: It was suggested that half hour before and after the end of administration respectively was the optimal period for sampling in the study of metabolism kinetics of amino acid by oral administration of 13C-leucine during feeding state.

Objective: To explore the plateau period of the enrichment of stable isotope for amino acid metabolism kinetics using the method of stable isotope tracer., Methods: Selecting 5 healthy adults as subject, all of them were given 13C labeled leucine for 3 hours by their cutaneous veins on day 6 after 5 days adaption period. The respired air was collected during the course of infusion and 1 hour after infusion to determine the enrichment of 13C., Results: The 13C enrichment in the respired air was at a higher level in 1 hour before infusion end and it will decrease immediately after the infusion end., Conclusion: It was suggested that one hour before infusion end is the optimal time for sampling in the study of metabolism kinetics of amino acid.

Objective: To investigate the effects of superoxide dismutase (SOD) and reducing iron load on experimental immunological liver injury in rat., Methods: 48 male Wistar rats were divided into six groups randomly. The animal model of iron low-load was created by intravasation of deferoxamine (DFO) or phlebotomy respectively. Immunological liver damage model was reproduced by injection of lipopolysaccharide (LPS) and BCG (Bacilli Calmette Guerin). The following parameters were determined such as serum iron (SI), transferrin (TRF) concentration, total proteins (TP) volume, the serum activities of aspartate aminotransferase (AST), and malondialdehyde (MDA) content, the activities of superoxide dismutase and iron deposition (HIC) in liver tissue extracts., Results: In comparison with blank control group, the SI levels lowered (P < 0.05) in pure DFO group, pure phlebotomy group and liver injury group. Compared with each own control groups, the serum activities of AST in all injury groups augmented and the levels of TP in them reduced significantly. The increased magnitude of the activities of AST and the decreased magnitude of TP levels in DFO injury group and phlebotomy injury group were less than those of pure injury group (P < 0.05). In comparison with the control group, the MDA levels in pure DFO and phlebotomy groups declined significantly and the activities of SOD in them had no significant difference. Compared with each own control groups, the MDA levels augmented and the activities of SOD reduced significantly in all injury groups., Conclusion: SOD activity reduces in immunological liver injury in rat. Iron low-load can mitigate the severity of liver injury.