SLC30A3 and SEP15 gene polymorphisms influence the serum concentrations of zinc and selenium in mature adults

Genetic Determinants of Selenium Availability, Selenium-Response, and Risk of Polycystic Ovary Syndrome

Selenium is a trace element and its deficiency has been associated with the risk of PCOS, a multifactorial syndrome that affects a large number of women worldwide. Several databases and literature were searched to find out genetic variants of the genes involved in selenium uptake, metabolism, and regulation which may be significantly associated with the risk of PCOS through Se-related pathways. Genes that require selenium for their biological actions to perform were also shortlisted. A total of eighteen significantly associated genes with forty-four variants were identified as candidate variants that could play a potential role in the modulation of PCOS risk among the study population. The genetic variant distribution data was available in-house and was obtained through a GWAS study of the North India population. In silico tools were applied to understand the functional impact of these variants. Three variants namely LDLR (rs2228671), TNF (rs1041981), and SAA2 (rs2468844) are strongly associated with PCOS risk and have a functional impact on encoded protein. Certain variants of Se uptake genes such as DIO1, GPX2, TXNRD1, DIO2 and GPX3 are also significantly associated with the risk of PCOS development. "C" allele of the Se transporter gene SELENOP (rs9686343) significantly increases PCOS risk. Other potential genes require selenium for their biological actions and are involved in the inflammatory, antioxidant response, and energy homeostasis signaling pathways. Thus, genetic variants of the population may affect the Se availability in the body. Also, deficiency of Se effects may get modulated due to underlying genetic polymorphism of Se-associated genes. This information may be helpful in dosage adjustment of Se supplementation for a population in order to get maximum benefits.

Urinary metal profiles in mother-offspring pairs and their association with early dysglycemia in the International Hyperglycemia and Adverse Pregnancy Outcome Follow Up Study (HAPO-FUS)

BACKGROUND

Variations in dietary intake and environmental exposure patterns of essential and non-essential trace metals influence many aspects of human health throughout the life span.

OBJECTIVE

To examine the relationship between urine profiles of essential and non-essential metals in mother-offspring pairs and their association with early dysglycemia.

METHODS

Herein, we report findings from an ancillary study to the international Hyperglycemia and Adverse Pregnancy Outcome Follow-Up Study (HAPO-FUS) that examined urinary essential and non-essential metal profiles from mothers and offspring ages 10-14 years (1012 mothers, 1013 offspring, 968 matched pairs) from 10 international sites.

RESULTS

Our analysis demonstrated a diverse exposure pattern across participating sites. In multiple regression modelling, a positive association between markers of early dysglycemia and urinary zinc was found in both mothers and offspring after adjustment for common risk factors for diabetes. The analysis showed weaker, positive, and negative associations of the 2-h glucose value with urinary selenium and arsenic respectively. A positive association between 2-h glucose values and cadmium was found only in mothers in the fully adjusted model when participants with established diabetes were excluded. There was a high degree of concordance between mother and offspring urinary metal profiles. Mother-to-offspring urinary metal ratios were unique for each metal, providing insights into changes in their homeostasis across the lifespan.

SIGNIFICANCE

Urinary levels of essential and non-essential metals are closely correlated between mothers and their offspring in an international cohort. Urinary levels of zinc, selenium, arsenic, and cadmium showed varying degrees of association with early dysglycemia in a comparatively healthy cohort with a low rate of preexisting diabetes.

IMPACT STATEMENT

Our data provides novel evidence for a strong correlation between mother and offspring urinary metal patterns with a unique mother-to-offspring ratio for each metal. The study also provides new evidence for a strong positive association between early dysglycemia and urinary zinc, both in mothers and offspring. Weaker positive associations with urinary selenium and cadmium and negative associations with arsenic were also found. The low rate of preexisting diabetes in this population provides the unique advantage of minimizing the confounding effect of preexisting, diabetes related renal changes that would alter the relationship between dysglycemia and renal metal excretion.

Toenail zinc as a biomarker: Relationship with sources of environmental exposure and with genetic variability in MCC-Spain study

BACKGROUND

Toenails are commonly used as biomarkers of exposure to zinc (Zn), but there is scarce information about their relationship with sources of exposure to Zn.

OBJECTIVES

To investigate the main determinants of toenail Zn, including selected sources of environmental exposure to Zn and individual genetic variability in Zn metabolism.

METHODS

We determined toenail Zn by inductively coupled plasma mass spectrometry in 3,448 general population controls from the MultiCase-Control study MCC-Spain. We assessed dietary and supplement Zn intake using food frequency questionnaires, residential proximity to Zn-emitting industries and residential topsoil Zn levels through interpolation methods. We constructed a polygenic score of genetic variability based on 81 single nucleotide polymorphisms in genes involved in Zn metabolism. Geometric mean ratios of toenail Zn across categories of each determinant were estimated from multivariate linear regression models on log-transformed toenail Zn.

RESULTS

Geometric mean toenail Zn was 104.1 µg/g in men and 100.3 µg/g in women. Geometric mean toenail Zn levels were 7 % lower (95 % confidence interval 1-13 %) in men older than 69 years and those in the upper tertile of fibre intake, and 9 % higher (3-16 %) in smoking men. Women residing within 3 km from Zn-emitting industries had 4 % higher geometric mean toenail Zn levels (0-9 %). Dietary Zn intake and polygenic score were unrelated to toenail Zn. Overall, the available determinants only explained 9.3 % of toenail Zn variability in men and 4.8 % in women.

DISCUSSION

Sociodemographic factors, lifestyle, diet, and environmental exposure explained little of the individual variability of toenail Zn in the study population. The available genetic variants related to Zn metabolism were not associated with toenail Zn.

Genetic Aspects of Micronutrients Important for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), Crohn’s disease (CD) and ulcerative colitis (UC) are complex diseases whose etiology is associated with genetic and environmental risk factors, among which are diet and gut microbiota. To date, IBD is an incurable disease and the main goal of its treatment is to reduce symptoms, prevent complications, and improve nutritional status and the quality of life. Patients with IBD usually suffer from nutritional deficiency with imbalances of specific micronutrient levels that contribute to the further deterioration of the disease. Therefore, along with medications usually used for IBD treatment, therapeutic strategies also include the supplementation of micronutrients such as vitamin D, folic acid, iron, and zinc. Micronutrient supplementation tailored according to individual needs could help patients to maintain overall health, avoid the triggering of symptoms, and support remission. The identification of individuals’ genotypes associated with the absorption, transport and metabolism of micronutrients can modify future clinical practice in IBD and enable individualized treatment. This review discusses the personalized approach with respect to genetics related to micronutrients commonly used in inflammatory bowel disease treatment.

Association of SNPs in zinc transporter genes on seminal plasma zinc levels in humans

This study is to examine the effects of single nucleotide polymorphisms (SNPs) of SLC30A and SLC39A on seminal plasma zinc concentration. Blood and seminal plasma samples were collected from outpatients. SNPs of zinc transporters were analyzed by next Generation sequencing technology, and seminal plasma zinc concentration were determined by inductively coupled plasma optical emission spectrometry. Our date showed nine SNPs (SLC30A8 rs2466295, rs2466294, SLC30A10 c.-160 C>G, SLC39A8 rs9331, rs9705, rs151392, rs151393, SLC39A11 rs9912126, SLC39A14 rs1051708) were significantly associated with seminal plasma zinc concentration, and 14 SNPs (SLC30A8 rs2466295, rs2466294, SLC30A10 c.-160 C>G, SLC39A6 rs148550301, SLC39A8 rs9331, rs9705, rs151392, rs151393, SLC39A11 rs9912126, rs61736066, rs36041371 and SLC39A14 rs1051708, rs76963096, rs17060854) were found to be significantly associated with total zinc per ejaculate. The seminal plasma zinc concentrations and total zinc per ejaculate were associated with the number of SNPs, and decreased significantly when five SNPs (SLC39A8 rs9331, rs9705, rs151392, rs151393 and SLC39A14 rs1051708) were a combination of homozygous genotype. Our findings suggest that different zinc transporter SNPs may significantly affect seminal plasma zinc levels.

Association between zinc deficiency and cognitive decline in community-dwelling older adults

This is a cross-sectional study evaluating the association between zinc deficiency and cognitive decline in 591 community-dwelling older adults living in the cities of Campinas, Limeira, and Piracicaba-SP. Cognitive status was evaluated using the Cognitive Abilities Screening Instrument-CASI-S, considering a decline for scores <23 for those aged 60-69 and <20 for those aged ≥70 years. Among the evaluated cognitive domains, older adults with zinc deficiency had significantly lower mean scores on the memory test (p=0.018). For zinc deficiency, values below 70 µg/dL were considered for women and 74 µg/dL for men. The prevalence of zinc deficiency was 3.9%, and cognitive deficit was 9.4%, being significantly higher in those with zinc deficiency compared with those with normal serum zinc concentrations. In adjusted multiple logistic regression analysis, the factors that remained associated with cognitive decline were zinc deficiency (OR=3.80; 95%CI=1.30-11.12), low schooling level (OR=3.12; 95%CI=1.49-6.50), lack of a partner (OR=1.88; 95%CI=1.04-3.42), risk of malnutrition (OR=3.98; 95%CI=2.36-6.71), and a history of encephalic vascular accident (OR=2.70; 95%CI=1.04-6.98). Zinc deficiency was associated with the presence of cognitive decline in older adults. Actions in primary health care are necessary to prevent the deficiency of this nutrient.

Association between zinc deficiency and cognitive decline in community-dwelling older adults

Abstract This is a cross-sectional study evaluating the association between zinc deficiency and cognitive decline in 591 community-dwelling older adults living in the cities of Campinas, Limeira, and Piracicaba-SP. Cognitive status was evaluated using the Cognitive Abilities Screening Instrument-CASI-S, considering a decline for scores <23 for those aged 60-69 and <20 for those aged ≥70 years. Among the evaluated cognitive domains, older adults with zinc deficiency had significantly lower mean scores on the memory test (p=0.018). For zinc deficiency, values below 70 µg/dL were considered for women and 74 µg/dL for men. The prevalence of zinc deficiency was 3.9%, and cognitive deficit was 9.4%, being significantly higher in those with zinc deficiency compared with those with normal serum zinc concentrations. In adjusted multiple logistic regression analysis, the factors that remained associated with cognitive decline were zinc deficiency (OR=3.80; 95%CI=1.30-11.12), low schooling level (OR=3.12; 95%CI=1.49-6.50), lack of a partner (OR=1.88; 95%CI=1.04-3.42), risk of malnutrition (OR=3.98; 95%CI=2.36-6.71), and a history of encephalic vascular accident (OR=2.70; 95%CI=1.04-6.98). Zinc deficiency was associated with the presence of cognitive decline in older adults. Actions in primary health care are necessary to prevent the deficiency of this nutrient.

Whole Genome Interpretation for a Family of Five

Although best practices have emerged on how to analyse and interpret personal genomes, the utility of whole genome screening remains underdeveloped. A large amount of information can be gathered from various types of analyses via whole genome sequencing including pathogenicity screening, genetic risk scoring, fitness, nutrition, and pharmacogenomic analysis. We recognize different levels of confidence when assessing the validity of genetic markers and apply rigorous standards for evaluation of phenotype associations. We illustrate the application of this approach on a family of five. By applying analyses of whole genomes from different methodological perspectives, we are able to build a more comprehensive picture to assist decision making in preventative healthcare and well-being management. Our interpretation and reporting outputs provide input for a clinician to develop a healthcare plan for the individual, based on genetic and other healthcare data.

Comparison of novel single nucleotide polymorphisms of zinc transporters with zinc concentration in the human blood and vaginal tissues

The most important proteins regulating cellular zinc homeostasis belong to two protein families of zinc transporters, the solute carrier family 30 (SLC30A) and solute carrier family 39 (SLC39A). We aimed to identify single nucleotide polymorphisms (SNPs) of the SLC30A and SLC39A genes and its association with blood and vaginal tissue zinc levels since vaginal tissue zinc level may play a role in vaginal remodeling and pathological conditions of the vagina. Blood and vaginal tissue samples were collected from women undergoing surgery for benign gynecological reasons. SNPs of twenty-four zinc transporters were determined by PCR/Sequence method, and the concentration of zinc was assessed by inductively coupled plasma optical emission spectrometry. Sequencing of selected exons revealed 16 SNPs, including five previously unidentified SNPs. Our data showed an association between the number of SNPs (more than six SNPs vs. less than six) per patient and high zinc vaginal tissue levels (67% vs. 33%, p < 0.01). The SLC39A4 SNP 590c A (rs17855765) was significantly more frequent in the group of women with high zinc vaginal tissue levels compared to the group without SNP (93% vs. 7%, p = 0.02). Also, our analysis revealed that the number of SNPs in SLC39A4 was significantly more frequent in patients with low zinc blood levels (76% vs. 24%, p = 0.01). Our findings indicate that different SNPs of the zinc transporter genes may have a significant effect on the blood and vaginal tissue zinc levels.

Association of SNPs in genes encoding zinc transporters on blood zinc levels in humans

Zinc homeostasis in cells depends on zinc transporters, which are divided into 2 families: ZnT (SLC30A) and ZIP (SLC39A). In this study, we examined the effect of 20 single nucleotide polymorphisms (SNPs) in 10 genes encoding zinc transporters on blood zinc concentration in Japanese subjects (n = 102). Blood zinc levels were determined by microwave plasma-atomic emission spectrometry, and SNPs were analyzed by polymerase chain reaction followed by restriction fragment length polymorphism analysis. Among the 20 SNPs examined, 3 SNPs (SLC30A3 rs11126936, SLC39A8 rs233804, and SLC39A14 rs4872479) were significantly associated with blood zinc concentration. Individuals with genotype TT and TG in rs11126936 showed significantly higher blood zinc concentrations than those with GG. As for rs233804, individuals harboring the A allele had significantly higher blood zinc concentrations than those without this allele. Furthermore, the genotype TT and TG in rs4872479 had significantly higher blood zinc concentrations than those with GG. Among these three SNPs, combination of SLC30A3 rs11126936 and SLC39A8 rs233804 may strongly affect blood zinc levels. This study is the first comprehensive investigation of the effect of SNPs in genes encoding zinc transporters on blood zinc concentration. Adverse effects of zinc deficiency are reported and above 3 SNPs may be related to genetic susceptibility to zinc deficiency.

The Effect of Ketogenic Diet on Serum Selenium Levels in Patients with Intractable Epilepsy

The aim of the present study was to evaluate serum selenium levels in children receiving olive oil-based ketogenic diet (KD) for intractable seizures for at least 1 year. Out of 320 patients who were initiated on KD, patients who continued receiving KD for at least 12 months were enrolled. Sixteen patients who had selenium deficiency at the time of starting KD were excluded. Finally, a total of 110 patients (mean age 7.3 ± 4.2 years) were included. Serum selenium levels were measured at baseline and at 3, 6, and 12 months after treatment initiation by using atomic absorption spectroscopy. Selenium deficiency was defined as a serum selenium level <48 μg/L at each visit. Repeated measure ANOVA with post hoc Bonferroni correction was used for data analysis. Mean duration of KD was 15.3 ± 4.3 months. Mean serum selenium levels were significantly lower at 6 and 12 months of KD treatment (66.2 ± 23.3 and 57.2 ± 16.2 μg/L, respectively) compared to pre-treatment levels (79.3 ± 25.7 μg/L) (p = 0.001). On the other hand, selenium levels did not show any significant difference at 3 months of KD treatment (70.0 ± 21.2 μg/L) compared to baseline levels (p = 0.076). A total of 54 patients (49.1%) were diagnosed with selenium deficiency, and oral selenium medication was initiated for these patients. No relevant clinical findings were detected, and echocardiographic findings were normal in all patients. The decline of the serum selenium concentrations after 6 and 12 months of ketogenic diet suggests that patients on this highly prescriptive dietary treatment need close monitoring of this trace element.

Genetic Variations as Modifying Factors to Dietary Zinc Requirements-A Systematic Review

Due to reduced cost and accessibility, the use of genetic testing has appealed to health professionals for personalising nutrition advice. However, translation of the evidence linking polymorphisms, dietary requirements, and pathology risk proves to be challenging for nutrition and dietetic practitioners. Zinc status and polymorphisms of genes coding for zinc-transporters have been associated with chronic diseases. The present study aimed to systematically review the literature to assess whether recommendations for zinc intake could be made according to genotype. Eighteen studies investigating 31 Single Nucleotide Polymorphisms (SNPs) in relation to zinc intake and/or status were identified. Five studies examined type 2 diabetes; zinc intake was found to interact independently with two polymorphisms in the zinc-transporter gene SLC30A8 to affect glucose metabolism indicators. While the outcomes were statistically significant, the small size of the effect and lack of replication raises issues regarding translation into nutrition and dietetic practice. Two studies assessed the relationship of polymorphisms and cognitive performance; seven studies assessed the association between a range of outcomes linked to chronic conditions in aging population; two papers described the analysis of the genetic contribution in determining zinc concentration in human milk; and two papers assessed zinc concentration in plasma without linking to clinical outcomes. The data extracted confirmed a connection between genetics and zinc requirements, although the direction and magnitude of the dietary modification for carriers of specific genotypes could not be defined. This study highlights the need to summarise nutrigenetics studies to enable health professionals to translate scientific evidence into dietary recommendations.

Role of SEP15 Gene Polymorphisms in the Time of Progression to AIDS

AIMS

HIV infection is a chronic disease that requires intensive treatment in its later phases, including dietary supplementation. Several studies have suggested clinical improvements in patients with high levels of selenium, linking these levels with a longer progression to AIDS. The objective of this study was to verify the association of two polymorphisms in the SEP15 gene, which encodes a selenoprotein that is responsible for the transport of selenium in cells, with the time of progression to AIDS in HIV-1-infected patients.

METHODS

Blood samples were obtained from 139 HIV-1-positive individuals after they provided informed consent. DNA was isolated and genotyped using real-time polymerase chain reaction for the presence of SEP15 single nucleotide polymorphisms (rs5859 and rs561104). Questionnaires on sociodemographic features and behavior were answered, and the time of progression to AIDS was estimated based on a medical chart analysis.

RESULTS

The allelic and genotypic frequencies did not differ between rapid and nonrapid progressors; however, the presence of the AA genotype of the rs5859 polymorphism was associated with a shorter time of progression to AIDS compared with GG homozygotes (hazard ratio = 3.62, 95% CI = 1.55-8.43, p = 0.003).

CONCLUSION

These findings show the importance of genetic analysis of the SEP15 gene in individual patients with regard to predicting time of progression to AIDS.

Loss of synaptic Zn2+ transporter function increases risk of febrile seizures

Febrile seizures (FS) are the most common seizure syndrome and are potentially a prelude to more severe epilepsy. Although zinc (Zn(2+)) metabolism has previously been implicated in FS, whether or not variation in proteins essential for Zn(2+) homeostasis contributes to susceptibility is unknown. Synaptic Zn(2+) is co-released with glutamate and modulates neuronal excitability. SLC30A3 encodes the zinc transporter 3 (ZNT3), which is primarily responsible for moving Zn(2+) into synaptic vesicles. Here we sequenced SLC30A3 and discovered a rare variant (c.892C > T; p.R298C) enriched in FS populations but absent in population-matched controls. Functional analysis revealed a significant loss-of-function of the mutated protein resulting from a trafficking deficit. Furthermore, mice null for ZnT3 were more sensitive than wild-type to hyperthermia-induced seizures that model FS. Together our data suggest that reduced synaptic Zn(2+) increases the risk of FS and more broadly support the idea that impaired synaptic Zn(2+) homeostasis can contribute to neuronal hyperexcitability.

The 811 C/T polymorphism in the 3' untranslated region of the selenoprotein 15-kDa (Sep15) gene and breast cancer in Caucasian women

The 15-kDa selenoprotein (Sep15) is a selenocysteine-containing oxidoreductase in the endoplasmic reticulum that participates in disulfide-bond formation and protein folding control. The 3'-untranslated region (3'-UTR) contains two exclusively linked, polymorphic sites at positions 811 (C/T) and 1125 (G/A), which result in two functional haplotypes: 811C/1125G or 811T/1125A. The 811T/1125A variant occurs significantly more often in African-Americans as compared to Caucasians and has been linked to increased breast cancer risk in black women. We studied the 811C/T (rs5845) Sep15 gene polymorphism in 182 Caucasian women-83 breast cancer cases and 99 healthy controls-by pyrosequencing and polymerase chain reaction. Associations between allelic variants and clinico-pathological variables (e.g., age, stage of disease, tumor type, grading, and receptor status) were investigated. The genotype distribution in breast cancer patients (CC 63.9 %, CT 33.7 %, TT 2.4 %) and controls (69.7 %, CT 28.3 %, TT 2 %) showed no significant difference (OR 0.77, 95 % CI 0.41-1.42, p = 0.4). The overall low prevalence of the T allele was in accordance with that reported for Caucasians in previous studies. There was no significant association between 811C/T Sep15 polymorphism and any of clinico-pathological parameters. In conclusion, we are the first to report on 811C/T SEP 15 polymorphism in white breast cancer patients. Genotype variation within the 3'-UTR of the SEP 15 gene showed no association with breast cancer risk or clinico-pathological parameters in Caucasian women.