Effect Of Vitamin A Deficiency On Liver Iron Metabolism And Its Mechanic Research

PartⅠCorrelation between Vitamin A Nutritional Status and Iron Metabolic HomeostasisObjective: To investigate the correlation between vitamin A nutritional status of preschool children and iron metabolic homeostasis and the total body iron content, as well as to evaluate the odds ratio of anemia and deficient iron storage by vitamin A status with cross-sectional descriptive study..Subjects and methods: Preschool children in four pre-school institutions were randomly chosen from the 20 kindergartens in Yudong Town, Banan District with cluster and stratified sampling method. The total children in one institution were planed to recruitment into present study as a whole. Simultaneously, children's demographic data, socio-economic status and eating habits, etc. were investigated by questionnaires. The concentration of serum vitamin A was measured by high-performance liquid chromatography (HPLC), serum ferritin (SF) by enzyme-linked immunosorbent assay (ELISA), serum transferring receptor (sTfR) by microparticle-enhanced immunoassay, C-reactive protein (CRP) by particle-enhanced immunoturbidimetry and hemoglobin (HB) by hemiglobincyanide. The sTfR-SF index (TFR-F index) and total body iron content were computed, respectively.Result: A total of 471 preschool children, 236 for boys and 235 for girls, were included in the cross-sectional study with age range from 2 to 7 years old with average age (4.0±0.85) (means±standard deviation) yrs. The concentrations of HB, SF, sTfR, serum vitamin A, TFR-F index and total body iron content were (115.8±9.2)g/L, (24.75±14.71)μg/L, (1.28±0.33)mg/L, (1.21±0.36)μmol/L, 0.9595(0.7257,1.2226) [media (P25, P75)] and 8.868 (6.986,10.470) mg/kg, respectively. The prevalence of anemia, deficient iron storage, vitamin A deficiency (VAD) and suspect sub-clinic vitamin A deficiency (SSVAD) were 23.5%, 45.1%, 6.5% and 26.0, respectively. After adjustment for the age, gender, different sources of kindergarten, family economic situation and dietary pattern, etc. the partial correlation coefficient (radjust) between vitamin A and HB, log SF, sTfR, TFR-F index and total body iron content were 0.16 (p<0.001), -0.13 (p=0.037), 0.17 (p=0.0011), -0.013 (p=0.7935) and -0.05 (p=0.3652), respectively. With a multiple logistic regression model, VAD was an independent risk factor for prevalence of deficient iron storage [(odds ratio, OR) (95% CI): 1.88(1.01, 2.97)] defined by SF but not a risk factor [OR (95% CI): 1.365(0.286, 6.513)] when defined by TFR-F index. Also, VAD was a independent risk factor for the prevalence of anemia [OR (95% CI): 2.56(1.15, 5.70)], however, when adjusting for SF and sTfR, the OR value decreased [OR (95% CI): 1.53(1.01,1.88)].Conclusion:1 Serum vitamin A levels of preschool children was closely correlated with biochemical index reflecting body iron reserves and mobilization, while not iron absorption and body total iron contents.2 VAD is an independent risk factor for prevalence of deficient iron storage mainly by its impact on iron reserves and mobilization, but seldom by iron absorption.3 VAD is an independent risk factor for the prevalence of anemia, mainly by its impact on iron metabolism, while there may exist other ways.PartⅡEffects of Vitamin A, Vitamin A plus Iron and Multiple Micronutrient-Fortified Seasoning Powder on Iron metabolic HomeostasisObjective: To evaluate the effect of vitamin A, vitamin A plus iron and multiple micronutrient-fortified seasoning powder on iron metabolic homeostasis, as well as to evaluate the relative risk of anemia and iron deficient disease by interventional styles.Subjects and methods: This was a randomized, control and blinded interventional field trial. A total of 226 2-7 years old preschool children were recruited from three nurseries in the area, and they were randomly assigned into three different fortified diet groups for 6 months. The Group I was fortified with vitamin A; Group II and III were fortified with vitamin A plus iron and vitamin A plus iron, thiamine, riboflavin, folic acid, niacinamide, zinc and calcium, respectively. The concentration of serum vitamin A was measured by high-performance liquid chromatography (HPLC), serum ferritin (SF) by enzyme-linked immunosorbent assay (ELISA), serum transferring receptor (sTfR) by microparticle-enhanced immunoassay, C-reactive protein (CRP) by particle-enhanced immunoturbidimetry and hemoglobin (HB) by hemiglobincyanide and sTfR-SF index (TFR-F index) and total body iron content were computed, respectively before and after intervention. Simultaneously, children's demographic data, socio-economic status and eating habits, etc were investigated by questionnaires.Result: The levels of HB and serum vitamin A significantly increased after intervention in all groups (p<0.05) but no marked difference was observed between groups (p>0.05) for HB while vitamin A levels in group Ⅱand groupⅢwere higher than that of groupⅠ. The levels of SF and sTfR significantly decreased after intervention in all groups (p<0.05) especially in groupⅡand groupⅢfor SF (p<0.05) and groupⅠfor sTfR (p<0.05). No marked change of TFR-F index and total body iron contents was observed in groupⅠ(p>0.05), while TFR-F index decreased and total body iron contents increased in groupⅡand groupⅢ(p<0.05) after intervention. After adjustment for the age, gender, different sources of kindergarten, family economic situation, passive smoking exposure and dietary pattern, etc, no interventional styles was a prominent protective factor of the risk for anemia and deficient iron storage defined by SF (p<0.05). Compared to vitamin A intervention, vitamin A + iron and multiple micronutrients supplementation were significant protective factor for deficient iron storage defined by TFR-F index [(relative risk, RR) (95% CI): 0.410(0.218, 0.992)].Conclusion:1 Vitamin A intervention has significant effect on iron storage and mobilization.2 Vitamin A intervention has no significant effect on TFR-F index and total body iron contents which prompted the possibility of seldom effect of vitamin A on iron absorption in small intestine.3 The combination of vitamin A and other micronutrients might be a better intervention for the improvement of iron deficiency for preschool-children.PartⅢEffect of Vitamin A Status on Rat Liver Iron Metabolic mode and Its MechanismObjective: To evaluate the effect of vitamin A status on erythrocyte index and to measure the expressions of the components of iron responsive element-iron regulated protein mode (IRE-IRP mode) and hepcidin- ferroportin (Hepc-FPN mode) in liver on mRNA and protein levels by vitamin A status.Method: About 30 healthy female Witster rats were randomly divided into vitamin A normal feeding group (NVA group, n = 10), vitamin A deficient feeding group (VAD group, n = 10) and vitamin A interventional group (VAI group, n=10) on which were fed forage including vitamin A 6500 IU/Kg and 400 IU/Kg, respectively from 3 weeks before and throughout pregnancy and lactation. In VAI group the mothers received VAD diet till post partum, and then received normal diet. The offspring were given low-dose vitamin A from postnatal and received normal diet after 4 weeks. The pups received the same diets as their mothers both before and after weaning until 8 weeks and 20 pups were randomly chosen from the three groups (two pups in each clutch with equal male and female) to measure the concentration of serum retinol by HPLC, levels of hemoglobin (HB), red blood cell (RBC), hematocrit (Hct), red cell distribution width (RDW), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) by automatic blood cytoanalyze. Moreover, the expressions of the components of IRE-IRP mode and Hepc-FPN mode in liver with mRNA and protein levels by fluorescent quantitation PCR, western blotting and euzymelinked immunosorbent assay (ELISA).Result: At eight week, the levels of HB, RBC and Hct in VAI group were significantly higher than that of NVA and VAD group (p<0.05). And the value of MCV was markedly lower than that of the other two group (p<0.05) and RDW was higher in VAI group (p<0.05), MCHC lower in VAI group (p<0.05). No significant difference of MCH was found among the three groups (p>0.05). Moreover, hepcidin, bone morphogenetic protein-4 and interleukin-6, iron regulatory protein-1, ferroportin-1, ferritin light chain and transferrin receptor-1 about components of iron metabolism presented different expression of mRNA and protein levels in liver by vitamin A status but not divalent metal transporter-1.Conclusion:1 Peripheral blood presented hypochromic microcytic by vitamin A deficiency which could be improved by vitamin A intervention and vitamin A deficiency showed no effect on MCH and MCHC.2 Iron Hepc-FPN mode in liver could be affected by vitamin A status by transcriptional regulation of IL-6 and BMP-4 on hepcidin expression.3 Iron IRP-IRE mode in liver could be affected by vitamin A status by transcriptional regulation on IRP-1 expression.