Localisation of iron and zinc in grain of biofortified wheat

The dietary contributions of iron (Fe) and zinc (Zn) from cereals are determined by concentrations, locations and chemical forms. A genetically biofortified wheat line showed higher concentrations of Zn and Fe than three control lines when grown over two years. The mineral distributions determined using imaging (histochemical staining and LA-ICP-MS), sequential pearling and hand dissection showed no consistent differences between the two lines. Fe was most abundant in the aleurone layer and the scutellum and Zn in the scutellar epithelium, the endosperm transfer cells and embryonic axis. Pearling fractions showed positive correlations between the concentration of P and those of Zn and Fe in all fractions except the outermost layer. This is consistent with Fe and Zn being concentrated in phytates. Developing grains showed decreasing gradients in concentration from the proximal to the distal ends. The concentrations of Fe and Zn were therefore higher in the biofortified line than the control lines but their locations did not differ

Localisation of iron and zinc in grain of biofortified wheat

The dietary contributions of iron (Fe) and zinc (Zn) from cereals are determined by concentrations, locations and chemical forms. A genetically biofortified wheat line showed higher concentrations of Zn and Fe than three control lines when grown over two years. The mineral distributions determined using imaging (histochemical staining and LA-ICP-MS), sequential pearling and hand dissection showed no consistent differences between the two lines. Fe was most abundant in the aleurone layer and the scutellum and Zn in the scutellar epithelium, the endosperm transfer cells and embryonic axis. Pearling fractions showed positive correlations between the concentration of P and those of Zn and Fe in all fractions except the outermost layer. This is consistent with Fe and Zn being concentrated in phytates. Developing grains showed decreasing gradients in concentration from the proximal to the distal ends. The concentrations of Fe and Zn were therefore higher in the biofortified line than the control lines but their locations did not differ

Impact of an SLC30A8 loss-of-function variant on the pancreatic distribution of zinc and manganese: laser ablation-ICP-MS and positron emission tomography studies in mice

IntroductionCommon variants in the SLC30A8 gene, encoding the secretory granule zinc transporter ZnT8 (expressed largely in pancreatic islet alpha and beta cells), are associated with altered risk of type 2 diabetes. Unexpectedly, rare loss-of-function (LoF) variants in the gene, described in heterozygous individuals only, are protective against the disease, even though knockout of the homologous SLC30A8 gene in mice leads to unchanged or impaired glucose tolerance. Here, we aimed to determine how one or two copies of the mutant R138X allele in the mouse SLC30A8 gene impacts the homeostasis of zinc at a whole-body (using non-invasive 62Zn PET imaging to assess the acute dynamics of zinc handling) and tissue/cell level [using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to map the long-term distribution of zinc and manganese in the pancreas].MethodsFollowing intravenous administration of [62Zn]Zn-citrate (~7 MBq, 150 μl) in wild-type (WT), heterozygous (R138X+/−), and homozygous (R138X+/+) mutant mice (14–15 weeks old, n = 4 per genotype), zinc dynamics were measured over 60 min using PET. Histological, islet hormone immunohistochemistry, and elemental analysis with LA-ICP-MS (Zn, Mn, P) were performed on sequential pancreas sections. Bulk Zn and Mn concentration in the pancreas was determined by solution ICP-MS.ResultsOur findings reveal that whereas uptake into organs, assessed using PET imaging of 62Zn, is largely unaffected by the R138X variant, mice homozygous of the mutant allele show a substantial lowering (to 40% of WT) of total islet zinc, as anticipated. In contrast, mice heterozygous for this allele, thus mimicking human carriers of LoF alleles, show markedly increased endocrine and exocrine zinc content (1.6-fold increase for both compared to WT), as measured by LA-ICP-MS. Both endocrine and exocrine manganese contents were also sharply increased in R138X+/− mice, with smaller increases observed in R138X+/+ mice.DiscussionThese data challenge the view that zinc depletion from the beta cell is the likely underlying driver for protection from type 2 diabetes development in carriers of LoF alleles. Instead, they suggest that heterozygous LoF may paradoxically increase pancreatic β-cell zinc and manganese content and impact the levels of these metals in the exocrine pancreas to improve insulin secretion