Expression of metallothionein in the liver and kidney of rats is influenced by excess dietary histidine

Safety and efficacy of l-histidine monohydrochloride monohydrate produced by fermentation with Escherichia coli (NITE BP-02526) for all animal species

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on l‐histidine monohydrochloride monohydrate produced by fermentation with Escherichia coli (NITE BP‐02526) when used as a nutritional additive or as a feed flavouring compound in feed and water for drinking for all animal species. The product under assessment is l‐histidine HCl H₂O produced by fermentation with a genetically modified strain of E. coli (NITE BP‐02526). The production strain and its recombinant DNA were not detected in the final products. l‐Histidine HCl H₂O does not give rise to any safety concern to the production strain. The use of l‐histidine HCl H₂O is safe for the target species when used to supplement the diet in appropriate amounts. It is safe at the proposed use level of 25 mg/kg when used as a flavouring compound for all animal species. The use of l‐histidine HCl H₂O in animal nutrition raises no safety concerns for consumers of animal products. The additive is not irritating to the skin or eyes and is not a skin sensitiser. There is a risk for persons handling the additive from the exposure to endotoxins by inhalation. The use of l‐histidine as a feed additive does not represent a risk to the environment. The additive l‐histidine HCl H₂O is regarded as an effective source of the amino acid l‐histidine when used as a nutritional additive. For the supplemental l‐histidine to be as efficacious in ruminants as in non‐ruminant species, it requires protection against degradation in the rumen. It is also considered efficacious as a feed flavouring compound under the proposed conditions of use.

Safety and efficacy of l-histidine monohydrochloride monohydrate produced using Corynebacterium glutamicum KCCM 80172 for all animal species

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on l-histidine monohydrochloride (HCl) monohydrate produced by fermentation using Corynebacterium glutamicum KCCM 80172 when used as a nutritional additive in feed and water for drinking for all animal species. The production strain is genetically modified. The production strain and its recombinant DNA were not detected in the final product. l-Histidine HCl monohydrate manufactured by fermentation using C. glutamicum KCCM 80172 does not give rise to any safety concern regarding the genetic modification. The use of l-histidine HCl monohydrate produced by fermentation using C. glutamicum KCCM 80172 is safe for the target species when used as a nutritional additive to supplement the diet in appropriate amounts to cover the requirements, depending on the species, the physiological state of the animal, the performance level, the environmental conditions, the background amino acid composition of the unsupplemented diet and the status of some essential trace elements such as copper and zinc. l-Histidine HCl monohydrate produced using C. glutamicum KCCM 80172 supplemented at levels appropriate for the requirements of the target species is considered safe for the consumer. l-Histidine HCl monohydrate produced using C. glutamicum KCCM 80172 is not irritant to skin, is a mildly irritant to eyes, and it is not a skin sensitiser. The additive does not pose a risk to users by inhalation. The use of l-histidine HCl monohydrate produced by C. glutamicum KCCM 80172 in animal nutrition is not expected to represent a risk to the environment. l-Histidine HCl monohydrate is considered an efficacious source of the essential amino acid l-histidine for non-ruminant animal species. For the supplemental l-histidine to be as efficacious in ruminants as in non-ruminant species, it would require protection against degradation in the rumen.

Histidine supplementation suppresses food intake and fat accumulation in rats

OBJECTIVE

Histamine, a derivative of histidine, decreases food intake and body fat by activation of histamine neurons. Our objective was to clarify the effect of dietary histidine, in particular, on food intake and/or body fat accumulation in rats.

METHODS

Male Wistar rats were assigned to one of four groups after acclimation and allowed free access to diets containing 20% casein (0% histidine), 20% casein plus 1.0% histidine, 20% casein plus 2.5% histidine, or 20% casein plus 5% histidine for 8 d.

RESULTS

Food intake and body weight were recorded daily and compared between groups. During the experimental period, food intake decreased according to the increases in dietary histidine. There was a negative and significant (P < 0.01) correlation between dietary histidine (grams per 8 d) and retroperitoneal fat pad (grams per 100 g of body weight). Uncoupling protein-1 mRNA in brown adipose tissue increased with increases in dietary histidine.

CONCLUSION

Our results indicate that dietary histidine suppresses food intake and fat accumulation in rats.

Manganese causes differential regulation of glutamate transporter (GLAST) taurine transporter and metallothionein in cultured rat astrocytes

Neurotoxicity due to excessive brain manganese (Mn) can occur due to environmental (air pollution, soil, water) and/ or metabolic aberrations (decreased biliary excretion). Manganese is associated with oxidative stress, as well as alterations in neurotransmitter metabolism with concurrent neurobehavioral deficits. Based on the few existing studies that have examined brain regional [Mn], it is likely that in pathological conditions it can reach 100-500 microM. Amino acid (e.g. aspartate, glutamate, taurine), as well as divalent metal (e.g. zinc, manganese) concentrations are regulated by astrocytes in the brain. Recently, it has been reported that cultured rat primary astrocytes exposed to Mn displayed decreased glutamate uptake, thereby, increasing the excitotoxic potential of glutamate. Since the neurotoxic mechanism(s) Mn employs in terms of glutamate metabolism is unknown, a primary goal of this study was to link altered glutamate uptake in Mn exposed astrocytes to alterations in glutamate transporter message. Further, we wanted to examine the gene expression of metallothionein (MT) and taurine transporter (tau-T) as markers of Mn exposure. Glutamate uptake was decreased by nearly 40% in accordance with a 48% decrease in glutamate/aspartate transporter (GLAST) mRNA. Taurine uptake was unaffected by Mn exposure even though tau-T mRNA increased by 123%. MT mRNA decreased in these Mn exposed astrocytes possibly due to altered metal metabolism, although this was not examined. These data show that glutamate and taurine transport in Mn exposed astrocytes are temporally different.

Glutamate/aspartate transporter (GLAST), taurine transporter and metallothionein mRNA levels are differentially altered in astrocytes exposed to manganese chloride, manganese phosphate or manganese sulfate

Manganese (Mn)-induced neurotoxicity can occur due to environmental exposure (air pollution, soil, water) and/or metabolic aberrations (decreased biliary excretion). High brain manganese levels lead to oxidative stress, as well as alterations in neurotransmitter metabolism with concurrent neurobehavioral deficits. Based on the few existing studies that have examined brain regional Mn concentration, it is likely that in pathological conditions, Mn concentration can reach between 100 and 500 microM. Environmental Mn exposure as a result of methylcyclopentadienyl manganese tricarbonyl (MMT) combustion is in the form of phosphate or sulfate (MnPO4, MnSO4, respectively). Pharmacokinetic studies have shown that the Mn salt will determine the rate of transport into the brain: MnCl2 > MnSO4 > MnPO4. The salt-specific neurotoxicity of these species is unknown. The primary goal of this study was to examine gene expression of glutamate/aspartate transporter (GLAST), taurine transporter (tau-T), and metallothionein-I (MT-I) in astrocytes exposed to manganese chloride (MnCl2), manganese sulfate (MnSO4), and manganese phosphate (MnPO4). We hypothesized that the effects of MnPO4 and MnSO4 exposure on GLASTexpression in astrocytes would be similar to those induced by MnCl2, since irrespective of salt species exposure, once internalized by astrocytes, the Mn ion would be identically complexed. At the same time, we hypothesized that the magnitude of the effect would be salt-dependent, since the chemical speciation would determine the rate of intracellular uptake of Mn. MnCl2 caused a significant overall decrease (P < 0.0001) in astrocytic GLAST mRNA levels with MnSO4 causing a moderate decrease. MnPO4 exposure did not alter GLAST mRNA in astrocytes. We also sought to examine astrocytic metallothionein and taurine transporter gene expression as markers of manganese exposure. Our findings suggest that manganese chloride significantly decreased (P < 0.0001) astrocytic metallothionein mRNA compared to both the sulfate and phosphate species. However, astrocytic taurine transporter mRNA was not affected by Mn exposure, irrespective of the salt species. These data are consistent with the hypothesis that astrocytic neurotoxicity due to Mn exposure is dependent upon its species, with solubility, and by inference, intracellular concentration, representing a major determinant of its neurotoxicity.