Influence Of Different Manganese Sources On Manganese Transport And Its Mechanism In Rats

The study included two experiments. The first one was conducted to invetigate the effects of dietary Fe level on the absorption of manganese (Mn) from manganese lysine complexes (MnLys) or Mn sulfate (MnSO4) in rats. Secondly, the primary rat intestinal epithelial cells culture model was established and was used to determine potential transporters involved in the uptake of Mn from MnLys in the small intestine of rats.Experiment 1:dietary Fe level on the absorption of Mn from MnLys or MnSO4 in ratsA total of 5421-d-old weaned male Sprague Dawley rats (body weight mean, 55.9 ± 4.3 g) were randomly divided into 6 treatments in a 2×3 factorial design with 9 replicates each treatment. Dietary Fe levels included the low Fe level (2.63 mg/kg, L-Fe), adequate Fe level (32.91 mg/kg, A-Fe) and high Fe level (179.69 mg/kg, H-Fe); dietary Mn sources included MnS04 (M) and MnLys (L) with 10 mg Mn/kg diet addition. Thus the 6 treatments were as follows:ML-Fe, LL-Fe, MA-Fe, LA-Fe, MH-Fe and LH-Fe. The rats were fed the diet with different Fe level and Mn source for 21 days. The results were as follows:1) MnLys increased (P< 0.001) the concentration of Mn in duodenum and plasma of rats compared with MnSO4. The Mn concentration in duodenum and plasma was higher (P< 0.05) in L-Fe than in A-Fe or H-Fe, but no signicant difference was found (P> 0,13) in above indice among LA-Fe, LH-Fe, and ML-Fe groups. Dietary Fe level, Mn source and their interaction had no significant effect on Mn concentration in liver of rats.2) In comparison with L-Fe treatment, H-Fe and A-Fe diet decreased (P< 0.01) the abundance of divalent metal transporter 1 (DMT1) mRNA. The Mnlys decreased (P< 0.05) DMT1 mRNA level in duodenum of rats fed with A-Fe diet when compared with MnSO4. However, no significant difference was found (P> 0.10) between MnLys and MnSO4 in duodenum of rate fed with L-Fe or H-Fe diet. Dietary Fe level, Mn source, and their interaction had no significant effect (P> 0.12) on the ferroportinl (FPN1) mRNA expression.3) DMT1 and FPN1 mRNA levels in liver of rats were lower (P< 0.05) in H-Fe treatment than in L-Fe treatment. The MnLys decreased (P< 0.05) hepatic DMT1 mRNA level as compared with MnSO4 in rats fed with H-Fe diet, but no significant difference was found in hepatic DMT1 mRNA level in rats fed with L-Fe or A-Fe diet.4) H-Fe diet decreased (P< 0.05) the protein level of duodenal DMT1 and FPN1, and hepatic DMT1 when compared with L-Fe, but no significant difference was found in hepatic FPN1 protein expression. The MnLys decreased (P< 0.05) the proetein expression of duodenal DMT1 and FPN1, and hepatic DMT1 compared with MnSO4 in rats fed with H-Fe diet. These results suggested that MnLys was more available than MnSO4 for rats. The DMT1 and FPN1 involved in Mn2+transport play a role in the absorption of Mn from MnLys complex in the duodenum of rats.Experiment 2:uptake of manganese as MnLys in the primary rat intestinal epithelial cell culturesThis experiment was conducted to compare the differences of the uptake of Mn from MnLys and MnSO4, and determine the potential mechanisms of the uptake of Mn from MnLys. We first established the primary rat intestinal epithelial cell culture model and used it to determine the uptake of Mn from different Mn source. The MnLys increased (P< 0.001) Mn uptake when compared to MnSO4. The uptake of Mn decreased (P< 0.05) with added Fe concentration increasing in the medium regardless of Mn source. The MnLys decreased (P< 0.01) Mn2+efflux transporter FPN1 mRNA level, but did not influence (P> 0.06) Mn2+influx transporter DMT1 mRNA expression when compared to MnSO4. The results above indicated that the increase of Mn accumulation for MnLys at least partly was due to the decrease of Mn efflux by reduced FPN1 expression. The N-ethylmaleimide, as an A-lysine transport system y+ inhibitor, decreased (P< 0.001) the uptake of Mn from MnLys, but did not affect (P> 0.10) the uptake of Mn from MnSO4. The cycloheximide, as an L-lysine transport system b0,+activator, increased (P< 0.001) the uptake of Mn from MnLys, whereas also did not influence the uptake of Mn from MnSO4. The MnLys increased (P< 0.01) the system y+member cationic amino acid transporter (CAT) 1, and system b0’+ components rBAT and b0,+AT mRNA expression when compared to MnSO4. These results suggested that the uptake of Mn from MnLys complex might be transported by CAT1 and system b0’+, which was different from ionized Mn uptake pathway. In conclusion, the uptake of MnLys complex not only might be absorbed as Mn2+, but also appeared to be transported through CAT1 and system b0,+in primary rat intestinal epithelial cells.These results in two experiments showed that the absorption of Mn from MnLys was higher than that from MnSO4. It is possible that the Mn from MnLys complex was absorbed not only by the divalent Mn pathway, but also by L-lysine transport systems. The CAT1 and system b0,+may be involved in the uptake of Mn from MnLys in the duodenum of rats.