Unraveling the potential effects of non-synonymous single nucleotide polymorphisms (nsSNPs) on the Protein structure and function of the human SLC30A8 gene on type 2 diabetes and colorectal cancer: An In silico approach.

Background and aims: The single nucleotide polymorphisms (SNPs) in SLC30A8 gene have been recognized as contributing to type 2 diabetes (T2D) susceptibility and colorectal cancer. This study aims to predict the structural stability, and functional impacts on variations in non-synonymous SNPs (nsSNPs) in the human SLC30A8 gene using various computational techniques. Materials and methods: Several in silico tools, including SIFT, Predict-SNP, SNPs&GO, MAPP, SNAP2, PhD-SNP, PANTHER, PolyPhen-1,PolyPhen-2, I-Mutant 2.0, and MUpro, have been used in our study. Results: After data analysis, out of 336 missenses, the eight nsSNPs, namely R138Q, I141N, W136G, I349N, L303R, E140A, W306C, and L308Q, were discovered by ConSurf to be in highly conserved regions, which could affect the stability of their proteins. Project HOPE determines any significant molecular effects on the structure and function of eight mutated proteins and the three-dimensional (3D) structures of these proteins. The two pharmacologically significant compounds, Luzonoid B and Roseoside demonstrate strong binding affinity to the mutant proteins, and they are more efficient in inhibiting them than the typical SLC30A8 protein using Autodock Vina and Chimera. Increased binding affinity to mutant SLC30A8 proteins has been determined not to influence drug resistance. Ultimately, the Kaplan-Meier plotter study revealed that alterations in SLC30A8 gene expression notably affect the survival rates of patients with various cancer types. Conclusion: Finally, the study found eight highly deleterious missense nsSNPs in the SLC30A8 gene that can be helpful for further proteomic and genomic studies for T2D and colorectal cancer diagnosis. These findings also pave the way for personalized treatments using biomarkers and more effective healthcare strategies.

Cell-type-specific enhancement of deviance detection by synaptic zinc in the mouse auditory cortex.

Stimulus-specific adaptation is a hallmark of sensory processing in which a repeated stimulus results in diminished successive neuronal responses, but a deviant stimulus will still elicit robust responses from the same neurons. Recent work has established that synaptically released zinc is an endogenous mechanism that shapes neuronal responses to sounds in the auditory cortex. Here, to understand the contributions of synaptic zinc to deviance detection of specific neurons, we performed wide-field and 2-photon calcium imaging of multiple classes of cortical neurons. We find that intratelencephalic (IT) neurons in both layers 2/3 and 5 as well as corticocollicular neurons in layer 5 all demonstrate deviance detection; however, we find a specific enhancement of deviance detection in corticocollicular neurons that arises from ZnT3-dependent synaptic zinc in layer 2/3 IT neurons. Genetic deletion of ZnT3 from layer 2/3 IT neurons removes the enhancing effects of synaptic zinc on corticocollicular neuron deviance detection and results in poorer acuity of detecting deviant sounds by behaving mice.

Integrated pan-cancer genomic analysis reveals the role of SLC30A5 in the proliferation, metastasis, and prognosis of hepatocellular carcinoma.

Background: SLC30A5, a member of the solute transporter protein family, is implicated in tumorigenesis and cancer progression. This study aimed to explore the expression and prognostic significance of SLC30A family genes in pan-cancer, with a specific emphasis on SLC30A5 in hepatocellular carcinoma (HCC). Methods: Expression patterns and prognostic implications of SLC30A family genes were assessed across 33 cancer types, especially HCC. Co-expression analysis explored the relationship between SLC30A5 and immune cell infiltration, immune checkpoints, pathway molecules related to tumor angiogenesis and epithelial-mesenchymal transition (EMT). The role of SLC30A5 in HCC was evaluated through in vitro and in vivo assays, including CCK8 viability assay, EdU cell proliferation assay, colony formation assay, apoptosis assay, wound healing assay, transwell migration assay, and xenograft mouse model assay using Huh7 cells with targeted knockdown of SLC30A5. Results: SLC30A family genes exhibited overexpression in various tumors. In HCC, upregulation of SLC30A5 expression correlated with adverse prognosis. Significant associations were observed between SLC30A5 expression and immune cell infiltration, immune checkpoints, molecules involved in angiogenesis, and EMT. SLC30A5 overexpression was associated with advanced disease stages, higher histological grades, and vascular invasion. Single-cell RNA sequencing data (GSE112271) revealed notable SLC30A5 expression in malignant cells. In vitro and in vivo assays demonstrated that SLC30A5 knockdown in Huh7 cells reduced proliferation, migration, and invasion while promoting apoptosis. Conclusions: This study highlights the clinical relevance of SLC30A5 in HCC, emphasizing its role in cell proliferation and migration. SLC30A5 emerges as a promising candidate for a prognostic marker and a potential target in HCC.

Exome Sequence Analysis to Characterize Undiagnosed Family Segregating Motor Impairment and Dystonia.

Background: Hypermanganesemia with dystonia 1 (HMNDYT1) is a rare genetic disorder characterized by elevated blood manganese levels. This condition is associated with polycythemia, motor neurodegeneration with extrapyramidal features, and hepatic dysfunction, which can progress to cirrhosis in some patients. Materials and Methods: In this study, a consanguineous Saudi family with two affected individuals exhibiting symptoms of severe motor impairment, spastic paraparesis, postural instability, and dystonia was studied. Clinical and radiographic evaluations were conducted on the affected individuals. Whole exome sequencing (WES) was performed to diagnose the disease and to determine the causative variant underlying the phenotype. Moreover, Sanger sequencing was used for validation and segregation analysis of the identified variant. Bioinformatics tools were utilized to predict the pathogenicity of candidate variants based on ACMG criteria. Results: Exome sequencing detected a recurrent homozygous missense variant (c.266T>C; p.L89P) in exon 1 of the SLC30A10 gene. Sanger sequencing was employed to validate the segregation of the discovered variant in all available family members. Bioinformatics tools predicted that the variant is potentially pathogenic. Moreover, conservation analysis showed that the variant is highly conserved in vertebrates. Conclusions: This study shows that exome sequencing is instrumental in diagnosing undiagnosed neurodevelopmental disorders. Moreover, this study expands the mutation spectrum of SLC30A10 in distinct populations.

Zinc transporter ZnT3/Slc30a3 has a potential role in zinc ion influx in mouse oocytes.

Zinc is an essential trace element for various physiological functions, including reproduction. The influx/efflux of zinc ions is regulated by zinc transporters (Zip1-14 and ZnT1-8, 10). However, the precise roles of zinc transporters and zinc dynamics in reproductive functions are unknown. In this study, ZnT3/Slc30a3 gene knockout (KO) mice were used to analyze the role of ZnT3. In ZnT3 KO mice, intracellular zinc ions in oocytes/zygotes were significantly reduced compared to those in controls, and free zinc ions did not accumulate in the oocyte cytoplasm. However, fertilization of these oocytes and the average litter size were comparable to those of control mice. Our results suggest that ZnT3 plays an important role in the accumulation of zinc ions in oocytes but not in the developmental ability of mice. ZnT3 KO mice will be useful for examining zinc dynamics in oocytes and other tissues.

PHD2 enzyme is an intracellular manganese sensor that initiates the homeostatic response against elevated manganese.

Intracellular sensors detect changes in levels of essential metals to initiate homeostatic responses. But, a mammalian manganese (Mn) sensor is unknown, representing a major gap in understanding of Mn homeostasis. Using human-relevant models, we recently reported that: 1) the primary homeostatic response to elevated Mn is upregulation of hypoxia-inducible factors (HIFs), which increases expression of the Mn efflux transporter SLC30A10; and 2) elevated Mn blocks the prolyl hydroxylation of HIFs by prolyl hydroxylase domain (PHD) enzymes, which otherwise targets HIFs for degradation. Thus, the mammalian mechanism for sensing elevated Mn likely relates to PHD inhibition. Moreover, 1) Mn substitutes for a catalytic iron (Fe) in PHD structures; and 2) exchangeable cellular levels of Fe and Mn are comparable. Therefore, we hypothesized that elevated Mn directly inhibits PHD by replacing its catalytic Fe. In vitro assays using catalytically active PHD2, the primary PHD isoform, revealed that Mn inhibited, and Fe supplementation rescued, PHD2 activity. However, a mutation in PHD2 (D315E) that selectively reduced Mn binding without substantially impacting Fe binding or enzymatic activity resulted in complete insensitivity of PHD2 to Mn in vitro. Additionally, hepatic cells expressing full-length PHD2D315E were less sensitive to Mn-induced HIF activation and SLC30A10 upregulation than PHD2wild-type. These results: 1) define a fundamental Mn sensing mechanism for controlling Mn homeostasis-elevated Mn inhibits PHD2, which functions as a Mn sensor, by outcompeting its catalytic Fe, and PHD2 inhibition activates HIF signaling to up-regulate SLC30A10; and 2) identify a unique mode of metal sensing that may have wide applicability.

Elevated thyroid manganese reduces thyroid iodine to induce hypothyroidism in mice, but not rats, lacking SLC30A10 transporter.

Elevated manganese (Mn) accumulates in the brain and induces neurotoxicity. SLC30A10 is an Mn efflux transporter that controls body Mn levels. We previously reported that full-body Slc30a10 knockout mice (1) recapitulate the body Mn retention phenotype of humans with loss-of-function SLC30A10 mutations and (2) unexpectedly develop hypothyroidism induced by Mn accumulation in the thyroid, which reduces intra-thyroid thyroxine. Subsequent analyses of National Health and Nutrition Examination Survey data identified an association between serum Mn and subclinical thyroid changes. The emergence of thyroid deficits as a feature of Mn toxicity suggests that changes in thyroid function may be an underappreciated, but critical, modulator of Mn-induced disease. To better understand the relationship between thyroid function and Mn toxicity, here we further defined the mechanism of Mn-induced hypothyroidism using mouse and rat models. Slc30a10 knockout mice exhibited a profound deficit in thyroid iodine levels that occurred contemporaneously with increases in thyroid Mn levels and preceded the onset of overt hypothyroidism. Wild-type Mn-exposed mice also exhibited increased thyroid Mn levels, an inverse correlation between thyroid Mn and iodine levels, and subclinical hypothyroidism. In contrast, thyroid iodine levels were unaltered in newly generated Slc30a10 knockout rats despite an increase in thyroid Mn levels, and the knockout rats were euthyroid. Thus, Mn-induced thyroid dysfunction in genetic or Mn exposure-induced mouse models occurs due to a reduction in thyroid iodine subsequent to an increase in thyroid Mn levels. Moreover, rat and mouse thyroids have differential sensitivities to Mn, which may impact the manifestations of Mn-induced disease in these routinely used animal models.

Development of a live cell assay for the zinc transporter ZnT8.

Zinc is an essential trace element that is involved in many biological processes and in cellular homeostasis. In pancreatic ß-cells, zinc is crucial for the synthesis, processing, and secretion of insulin, which plays a key role in glucose homeostasis and which deficiency is the cause of diabetes. The accumulation of zinc in pancreatic cells is regulated by the solute carrier transporter SLC30A8 (or Zinc Transporter 8, ZnT8), which transports zinc from cytoplasm in intracellular vesicles. Allelic variants of SLC30A8 gene have been linked to diabetes. Given the physiological intracellular localization of SLC30A8 in pancreatic ß-cells and the ubiquitous endogenous expression of other Zinc transporters in different cell lines that could be used as cellular model for SLC30A8 recombinant over-expression, it is challenging to develop a functional assay to measure SLC30A8 activity. To achieve this goal, we have firstly generated a HEK293 cell line stably overexpressing SLC30A8, where the over-expression favors the partial localization of SLC30A8 on the plasma membrane. Then, we used the combination of this cell model, commercial FluoZin-3 cell permeant zinc dye and live cell imaging approach to follow zinc flux across SLC30A8 over-expressed on plasma membrane, thus developing a novel functional imaging- based assay specific for SLC30A8. Our novel approach can be further explored and optimized, paving the way for future small molecule medium-throughput screening.

Trans-synaptic Association of Vesicular Zinc Transporter 3 and Shank3 Supports Synapse-Specific Dendritic Spine Structure and Function in the Mouse Auditory Cortex.

Shank3 is a synaptic scaffolding protein that assists in tethering and organizing structural proteins and glutamatergic receptors in the postsynaptic density of excitatory synapses. The localization of Shank3 at excitatory synapses and the formation of stable Shank3 complexes is regulated by the binding of zinc to the C-terminal sterile-alpha-motif (SAM) domain of Shank3. Mutations in the SAM domain of Shank3 result in altered synaptic function and morphology, and disruption of zinc in synapses that express Shank3 leads to a reduction of postsynaptic proteins important for synaptic structure and function. This suggests that zinc supports the localization of postsynaptic proteins via Shank3. Many regions of the brain are highly enriched with free zinc inside glutamatergic vesicles at presynaptic terminals. At these synapses, zinc transporter 3 (ZnT3) moves zinc into vesicles where it is co-released with glutamate. Alterations in ZnT3 are implicated in multiple neurodevelopmental disorders, and ZnT3 knock-out (KO) mice-which lack synaptic zinc-show behavioral deficits associated with autism spectrum disorder and schizophrenia. Here we show that male and female ZnT3 KO mice have smaller dendritic spines and miniature excitatory postsynaptic current amplitudes than wildtype (WT) mice in the auditory cortex. Additionally, spine size deficits in ZnT3 KO mice are restricted to synapses that express Shank3. In WT mice, synapses that express both Shank3 and ZnT3 have larger spines compared to synapses that express Shank3 but not ZnT3. Together these findings suggest a mechanism whereby presynaptic ZnT3-dependent zinc supports postsynaptic structure and function via Shank3 in a synapse-specific manner.

AAV-mediated hepatic expression of SLC30A10 and the Thr95Ile variant attenuates manganese excess and other phenotypes in Slc30a10-deficient mice.

The manganese (Mn) export protein SLC30A10 is essential for Mn excretion via the liver and intestines. Patients with SLC30A10 deficiency develop Mn excess, dystonia, liver disease, and polycythemia. Recent genome-wide association studies revealed a link between the SLC30A10 variant T95I and markers of liver disease. The in vivo relevance of this variant has yet to be investigated. Using in vitro and in vivo models, we explore the impact of the T95I variant on SLC30A10 function. While SLC30A10 I95 expressed at lower levels than T95 in transfected cell lines, both T95 and I95 variants protected cells similarly from Mn-induced toxicity. Adeno-associated virus 8-mediated expression of T95 or I95 SLC30A10 using the liver-specific thyroxine binding globulin promoter normalized liver Mn levels in mice with hepatocyte Slc30a10 deficiency. Furthermore, Adeno-associated virus-mediated expression of T95 or I95 SLC30A10 normalized red blood cell parameters and body weights and attenuated Mn levels and differential gene expression in livers and brains of mice with whole body Slc30a10 deficiency. While our in vivo data do not indicate that the T95I variant significantly compromises SLC30A10 function, it does reinforce the notion that the liver is a key site of SLC30A10 function. It also supports the idea that restoration of hepatic SLC30A10 expression is sufficient to attenuate phenotypes in SLC30A10 deficiency.

Investigation of cuproptosis regulator-mediated modification patterns and SLC30A7 function in GBM.

BACKGROUND: Copper-dependent controlled cell death (cuproptosis) is a novel cell death modality that is distinct from known cell death mechanisms. Nonetheless, the potential role of the cuproptosis regulator in tumour microenvironment (TME) of GBM remains unknown. METHODS: Based on 13 widely recognised cuproptosis regulators, the cuproptosis regulation patterns and the biological characteristics of each pattern were comprehensively assessed in GBMs. Machine learning strategies were used to construct a CupScore to quantify the cuproptosis regulation patterns of individual tumours. A PPI network was constructed to predict core-associated genes of cuproptosis regulators. The function of the novel cuproptosis regulators SLC30A7 was examined by in vitro and in vivo experiment. RESULTS: We identified three distinct cuproptosis regulation patterns, including immune activation, metabolic activation, and immunometabolic double deletion patterns. The CupScore was shown to predict the abundance of tumour inflammation, molecular subtype, stromal activity, gene variation, signalling pathways, and patient prognosis. The low CupScore subtype was characterised by immune activation, isocitrate dehydrogenase mutations, sensitivity to chemotherapy, and clinical benefits. The high CupScore subtype was characterised by activation of the stroma and metabolism and poor survival. Novel cuproptosis regulator SLC30A7 knockdown inhibited the cuproptosi via JAK2/STAT3/ATP7A pathway in GBM. CONCLUSION: Cuproptosis regulators have been shown to play a vital role in TME complexity. Constructing CupScores were trained to evaluate the regulation patterns of cuproptosis in individual tumours. The novel cuproptosis-related genes SLC30A7 was involved in regulation the tumorigenicity of GBM cell via JAK2/STAT3/ATP7A pathway in vitro and in vivo.

Case Report: A rare form of congenital erythrocytosis due to SLC30A10 biallelic variants-differential diagnosis and recommendation for biochemical and genetic screening.

Congenital erythrocytosis recognizes heterogeneous genetic basis and despite the use of NGS technologies, more than 50% of cases are still classified as idiopathic. Herein, we describe the case of a 3-year-old boy with a rare metabolic disorder due to SLC30A10 bi-allelic mutations and characterized by hypermanganesemia, congenital erythrocytosis and neurodegeneration, also known as hypermanganesemia with dystonia 1 (HMNDYT1). The patient was treated with iron supplementation and chelation therapy with CaNa2EDTA, resulting in a significative reduction of blood manganese levels and erythrocytosis indexes. Although it couldn't be excluded that the patient's developmental impairment was part of the phenotypic spectrum of the disease, after three months from starting treatment no characteristic extrapyramidal sign was detectable. Our findings suggest the importance of assessing serum manganese levels in patients with unexplained polycythemia and increased liver enzymes. Moreover, we highlight the importance of extended genetic testing as a powerful diagnostic tool to uncover rare genetic forms of congenital erythrocytosis. In the described patient, identifying the molecular cause of erythrocytosis has proven essential for proper clinical management and access to therapeutic options.

Zinc Transporters Serve as Prognostic Predictors and their Expression Correlates with Immune Cell Infiltration in Specific Cancer: A Pan-cancer Analysis.

The disruption of zinc (Zn) homeostasis has been implicated in cancer development and progression through various signaling pathways. Maintaining intracellular zinc balance is crucial in the context of cancer. Human cells rely on two families of transmembrane transporters, SLC30A/ZNT and SLC39A/ZIP, to coordinate zinc homeostasis. While some ZNTs and ZIPs have been linked to cancer progression, limited information is available regarding the expression patterns of zinc homeostasis-related genes and their potential roles in predicting prognosis and developing therapeutic strategies for specific cancers. In this study, a systematic analysis was conducted to examine the expression of all genes from the SLC30A and SLC39A families at both mRNA and protein levels across different cancers. As a result, three SLC39A genes (SLC39A1, SLC39A4, and SLC39A8) were found to be significantly dysregulated in specific cancers, including cervical squamous cell carcinoma and endocervical adenocarcinoma (CESC), liver hepatocellular carcinoma (LIHC), pancreatic adenocarcinoma (PAAD), and kidney renal papillary cell carcinoma (KIRP). Moreover, the dysregulation of these genes was tightly associated with the prognosis of patients with those cancers. Furthermore, we found that the gene SLC39A8 exhibited the lowest mutation frequency in KIRP, whereas mutations in SLC39A4 were found to significantly impact overall survival (OS), disease-free (DF), and progress-free survival (PFS) in cancer patients, particularly in those with PAAD. Additionally, immune infiltration analysis revealed that SLC39A1, SLC39A4, and SLC39A8 may function as immune regulators in cancers. This provides new insights into understanding the complex relationship between zinc homeostasis and cancer progression.

Loss of SLC30A10 manganese transporter alters expression of neurotransmission genes and activates hypoxia-inducible factor signaling in mice.

The essential metal manganese (Mn) induces neuromotor disease at elevated levels. The manganese efflux transporter SLC30A10 regulates brain Mn levels. Homozygous loss-of-function mutations in SLC30A10 induce hereditary Mn neurotoxicity in humans. Our prior characterization of Slc30a10 knockout mice recapitulated the high brain Mn levels and neuromotor deficits reported in humans. But, mechanisms of Mn-induced motor deficits due to SLC30A10 mutations or elevated Mn exposure are unclear. To gain insights into this issue, we characterized changes in gene expression in the basal ganglia, the main brain region targeted by Mn, of Slc30a10 knockout mice using unbiased transcriptomics. Compared with littermates, >1000 genes were upregulated or downregulated in the basal ganglia sub-regions (i.e. caudate putamen, globus pallidus, and substantia nigra) of the knockouts. Pathway analyses revealed notable changes in genes regulating synaptic transmission and neurotransmitter function in the knockouts that may contribute to the motor phenotype. Expression changes in the knockouts were essentially normalized by a reduced Mn chow, establishing that changes were Mn dependent. Upstream regulator analyses identified hypoxia-inducible factor (HIF) signaling, which we recently characterized to be a primary cellular response to elevated Mn, as a critical mediator of the transcriptomic changes in the basal ganglia of the knockout mice. HIF activation was also evident in the liver of the knockout mice. These results: (i) enhance understanding of the pathobiology of Mn-induced motor disease; (ii) identify specific target genes/pathways for future mechanistic analyses; and (iii) independently corroborate the importance of the HIF pathway in Mn homeostasis and toxicity.

Epigenomic analysis of the myometrium during late implantation revealed regulatory elements in genes related to the cellular zinc homeostasis pathway in pigs.

The myometrium, composed of the inner circular muscle (CM) and outer longitudinal muscle (LM), is crucial in establishing and maintaining early pregnancy. However, the molecular mechanisms involved are not well understood. In this study, we identified the transcriptomic features of the CM and LM collected from the mesometrial (M) and anti-mesometrial (AM) sides of the pig uterus on day 18 of pregnancy during the placentation initiation phase. Some genes in the cellular zinc ion level regulatory pathways (MT-1A, MT-1D, MT-2B, SLC30A2, and SLC39A2) were spatially and highly enriched in uterine CM at the mesometrial side. In addition, the histone modification profiles of H3K27ac and H3K4me3 in uterine CM and LM collected from the mesometrial side were characterized. Genomic regions associated with the expression of genes regulating the cellular zinc ion level were detected. Moreover, six highly linked variants in the H3K27ac-enriched region of the pig SLC30A2 gene were identified and found to be significantly associated with the total number born at the second parity (P < 0.05). In conclusion, the genes in the pathways of cellular zinc homeostasis and their regulatory elements identified have implications for pig reproduction trait improvement and warrant further investigations.

Electrophysiological characterisation of iPSC-derived human ß-like cells and an SLC30A8 disease model.

iPSC-derived human ß-like cells (BLC) hold promise for both therapy and disease modelling, but their generation remains challenging and their functional analyses beyond transcriptomic and morphological assessments remain limited. Here, we validate an approach using multicellular and single cell electrophysiological tools to evaluate BLCs functions. The Multi-Electrode Arrays (MEAs) measuring the extracellular electrical activity revealed that BLCs are electrically coupled, produce slow potential (SP) signals like primary ß-cells that are closely linked to insulin secretion. We also used high-resolution single-cell patch-clamp measurements to capture the exocytotic properties, and characterize voltage-gated sodium and calcium currents. These were comparable to those in primary ß and EndoC-ßH1 cells. The KATP channel conductance is greater than in human primary ß cells which may account for the limited glucose responsiveness observed with MEA. We used MEAs to study the impact of the type 2 diabetes protective SLC30A8 allele (p.Lys34Serfs*50) and found that BLCs with this allele have stronger electrical coupling. Our data suggest that with an adapted approach BLCs from pioneer protocol can be used to evaluate the functional impact of genetic variants on ß-cell function and coupling.

Zinc intake, SLC30A8 rs3802177 polymorphism, and colorectal cancer risk in a Korean population: a case-control study.

PURPOSE: Zinc is an essential micronutrient involving in multiple enzymatic reactions of human metabolism and biological functions affecting the cancer development. However, the relationship between dietary zinc intake and colorectal cancer (CRC) risk has been unclear. Herein, our study investigated the relationship between dietary zinc intake and CRC risk, and examined how the SLC30A8 rs3802177 genetic variant affects this association. METHODS: A total of 1431 CRC cases and 2704 controls were selected to investigate the relationship between dietary zinc intake and CRC risk. After excluding individuals without genotype data, 1097 CRC cases and 1559 controls were used to evaluate the interaction between dietary zinc intake and the rs3802177 polymorphism in CRC risk. The odds ratios (ORs) and 95% confidence intervals (CIs) were measured using unconditional logistic regression models. RESULTS: Higher dietary zinc intake was inversely associated with the risk of CRC in the total population [adjusted OR (aOR) = 0.80, 95% CI 0.66-0.96, p for trend = 0.018]. In the codominant model, G+ carriers of the SLC30A8 rs3802177 with higher consumption of zinc were observed to have a significantly lower risk of CRC in all participants (p for interaction = 0.020). In females, GG carriers with higher zinc intake showed a stronger protective effect against the development of CRC (p for interaction = 0.008). CONCLUSIONS: In summary, our findings suggest an inverse association between dietary zinc intake and CRC risk, and this relationship may be modified by SLC30A8 rs3802177 polymorphism.

Synaptic zinc potentiates AMPA receptor function in mouse auditory cortex.

Synaptic zinc signaling modulates synaptic activity and is present in specific populations of cortical neurons, suggesting that synaptic zinc contributes to the diversity of intracortical synaptic microcircuits and their functional specificity. To understand the role of zinc signaling in the cortex, we performed whole-cell patch-clamp recordings from intratelencephalic (IT)-type neurons and pyramidal tract (PT)-type neurons in layer 5 of the mouse auditory cortex during optogenetic stimulation of specific classes of presynaptic neurons. Our results show that synaptic zinc potentiates AMPA receptor (AMPAR) function in a synapse-specific manner. We performed in vivo 2-photon calcium imaging of the same classes of neurons in awake mice and found that changes in synaptic zinc can widen or sharpen the sound-frequency tuning bandwidth of IT-type neurons but only widen the tuning bandwidth of PT-type neurons. These results provide evidence for synapse- and cell-type-specific actions of synaptic zinc in the cortex.

Hepatic and intestinal manganese excretion are both required to regulate brain manganese during elevated manganese exposure.

Manganese (Mn) is essential but neurotoxic at elevated levels. Under physiological conditions, Mn is primarily excreted by the liver, with the intestines playing a secondary role. Recent analyses of tissue-specific Slc30a10 or Slc39a14 knockout mice (SLC30A10 and SLC39A14 are Mn transporters) revealed that, under physiological conditions: 1) excretion of Mn by the liver and intestines is a major pathway that regulates brain Mn; and surprisingly, 2) the intestines compensate for loss of hepatic Mn excretion in controlling brain Mn. The unexpected importance of the intestines in controlling physiological brain Mn led us to determine the role of hepatic and intestinal Mn excretion in regulating brain Mn during elevated Mn exposure. We used liver- or intestine-specific Slc30a10 knockout mice as models to inhibit hepatic or intestinal Mn excretion. Compared with littermates, both knockout strains exhibited similar increases in brain Mn after elevated Mn exposure in early or later life. Thus, unlike physiological conditions, both hepatic and intestinal Mn excretion are required to control brain Mn during elevated Mn exposure. However, brain Mn levels of littermates and both knockout strains exposed to elevated Mn only in early life were normalized in later life. Thus, hepatic and intestinal Mn excretion play compensatory roles in clearing brain Mn accumulated by early life Mn exposure. Finally, neuromotor assays provided evidence consistent with a role for hepatic and intestinal Mn excretion in functionally modulating Mn neurotoxicity during Mn exposure. Put together, these findings substantially enhance understanding of the regulation of brain Mn by excretion.NEW & NOTEWORTHY This article shows that, in contrast with expectations from prior studies and physiological conditions, excretion of manganese by the intestines and liver is equally important in controlling brain manganese during human-relevant manganese exposure. The results provide foundational insights about the interorgan mechanisms that control brain manganese homeostasis at the organism level and have important implications for the development of therapeutics to treat manganese-induced neurological disease.

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.

Introduction: Common 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]. Methods: Following 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. Results: Our 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. Discussion: These 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 ß-cell zinc and manganese content and impact the levels of these metals in the exocrine pancreas to improve insulin secretion.