Improvement Of Nutritional Metabolism By Supplementation Of Vitamins B₁ , B₂ And Ppin Mice Exposed To Acute Hypoxia And Its Mechanisms Involved

ObjectiveTo observe the effects of vitamins B1, B2 and PP supplementation on the nutritional metabolism in mice exposed to acute hypoxia and explore the mechanisms possibly involved.Methods1. Male Kunming mice were fed vitamin B1, B2 and PP supplemented diets for two weeks. The contents of vitamins B1, B2 and PP in diets were increased 2,4 and 8 times as much as the basic diet contained, respectively. The survival time of mice was determined using sodium nitrite poisoning and acute hypoxia exposure methods.2. Fifty male Kunming mice were randomly divided into normal, acute hypoxia, acute hypoxia plus 2 times,4 times and 8 times vitamins B1, B2, PP supplemented groups. All mice were fed corresponding diets for two weeks and then all mice except the normal control were exposed to a simulated altitude of 6000 meters for 8 hours. The serum contents of vitamins B1, B2 and PP were measured using HPLC method. The serum contents of glucose, pyruvate, lactate, urea nitrogen, free fatty acids,β-hydroxybutyric acid, and blood ATP concentration, liver glycogen, and the activities of pyruvate dehydrogenase and succinate dehydrogenase were also determined.3.1H nuclear magnetic resonance analysis(1H NMR) was used to identify the changes of serum metabolic profiles.4. DNA microarray was used to analysis the hepatic profiles of gene expression.Results1. The acute hypoxia exposure test showed that the survival time of mice in 8 times vitamins B1, B2 and PP supplemented group were prolonged. The sodium nitrite poisoning test showed that the three vitamins supplemented groups had a longer survival time than the control. The survival time was significantly extended in 4 times and 8 times supplemented groups compared to control.2. After being exposed to acute hypoxia, the serum vitamin B1 content did not change remarkably while the vitamins B2 and PP were decreased significantly. The serum contents of glucose, pyruvate, lactate, free fatty acids,β-hydroxybutyric acid, urea nitrogen and hepatic glycogen were increased significantly while blood ATP concentration was decreased. The activities of hepatic pyruvate dehydrogenase and succinate dehydrogenase were also decreased significantly. After vitamins B1, B2 and PP supplementation, all changes mentioned above were improved.3. The results of metabolomic analysis showed that all serum samples from five groups were different in metabolic profiles and the scores plot indicated a clear metabolic trajectory, in which the hypoxia group moved away from the normal group after acute hypoxia exposure and returned back gradually after vitamins B1, B2, PP supplementation. The loadings plot showed that the acute hypoxia exposure induced a relative increase in the serum concentrations of lactate, sugar, lipids, choline, succinate, taurine, alanine, glutamine and decrease in ethanol, phosphocholine. After vitamins B1, B2, PP supplementation, all these metabolic changes were recovered to some extent.4. There were significant changes in hepatic profiles of gene expression in mice exposed to acute hypoxia and 8 times vitamins B1, B2 and PP supplementation. These different expressed genes were related to many metabolic pathways. Compared to the normal control, there were totally 2476 genes expressed differently after acute hypoxia exposed (1508 up regulated genes and 968 down regulated genes), which referred to 159 metabolic pathways and 2352 genes expressed differently in the acute hypoxia plus 8 times vitamins B1, B2 and PP supplementation group (1382 up regulated genes and 970 down graduated genes), which referred to 151 pathways. Compared to the hypoxia control group, there were 1382 genes differently expressed (626 up reregulated genes and 756 down regulated genes) in the acute hypoxia plus 8 times vitamins B1, B2 and PP supplementation group, which referred to 92 metabolic pathways.Conclusion1. The survival time of mice exposed to acute hypoxia could be prolonged after the supplementation of vitamin B1, B2 and PP. The effect of 4 to 8 times supplementation was better. 2. The serum vitamins B2 and PP contents were decreased after acute hypoxia exposure and improved by vitamins supplementation. The significant changes in carbohydrate, lipid and protein metabolisms after acute hypoxia exposure were also improved. The 8 times vitamins supplementation appeared to be better.3. The results of metabolomic analysis also demonstrated that vitamins supplementation improved the carbohydrate and lipid metabolisms significantly after acute hypoxia exposure. The serum metabolic profiles were returned to normal gradually.4. Many metabolic pathways were changed in the mice exposed to acute hypoxia and 8 times vitamins B1, B2 and PP supplementation, most of which were related to glycolytic pathway, pentose phosphate pathway, tricarboxylic acid cycle, fatty acid biosynthesis, lipid and lipoprotein metabolism, amino acids metabolism and electron transfer chain. These results indicated that the supplementation of vitamins Bi, B2 and PP could improve the nutritional metabolism partially through regulation of gene expression.