Glucose, Fructose, and Urate Transporters in the Choroid Plexus Epithelium

The choroid plexus plays a central role in the regulation of the microenvironment of the central nervous system by secreting the majority of the cerebrospinal fluid and controlling its composition, despite that it only represents approximately 1% of the total brain weight. In addition to a variety of transporter and channel proteins for solutes and water, the choroid plexus epithelial cells are equipped with glucose, fructose, and urate transporters that are used as energy sources or antioxidative neuroprotective substrates. This review focuses on the recent advances in the understanding of the transporters of the SLC2A and SLC5A families (GLUT1, SGLT2, GLUT5, GLUT8, and GLUT9), as well as on the urate-transporting URAT1 and BCRP/ABCG2, which are expressed in choroid plexus epithelial cells. The glucose, fructose, and urate transporters repertoire in the choroid plexus epithelium share similar features with the renal proximal tubular epithelium, although some of these transporters exhibit inversely polarized submembrane localization. Since choroid plexus epithelial cells have high energy demands for proper functioning, a decline in the expression and function of these transporters can contribute to the process of age-associated brain impairment and pathophysiology of neurodegenerative diseases.

Deiodinases, organic anion transporter polypeptide polymorphisms and symptoms of anxiety and depression after ischemic stroke

BACKGROUND

Emotional disturbances, such as anxiety and depression are common after acute ischemic stroke (AIS). Individual variation in emotional outcome is strongly influenced by genetic factors. One of pituitary axis, is the hypothalamic-pituitary-thyroid axis, a critical regulator of post-stroke recovery, suggesting that allelic variants in thyroid hormone (TH) signaling regulation can influence stroke outcome.

AIM

To determine associations between AIS emotional outcome and allelic variants of the TH metabolizing enzymes 1-3 type deiodinase (DIO1-3) and the membrane transporting organic anion polypeptide 1C1 (OATP1C1).

METHODS

Eligible AIS patients from Lithuania (n=168) were genotyped for ten DIO1-3 and OATP1C1 single nucleotide polymorphisms (SNP): DIO1 rs12095080-A/G, rs11206244-C/T, and rs2235544-A/C; DIO2 rs225014-T/C and rs225015-G/A; DIO3 rs945006-T/G; OATP1C1 rs974453-G/A, rs10444412-T/C, rs10770704-C/T, and rs1515777-A/G. Emotional outcome was evaluated using the Hospital Anxiety and Depression Scale at discharge from the neurology department after experienced index AIS.

RESULTS

After adjustment for potential confounders, the major allelic (wild-type) DIO1-rs12095080 genotype (AA) was associated with higher odds ratio of anxiety symptoms (OR = 5.16; 95% CI: 1.04-25.58; p = 0.045), conversely, DIO1-rs11206244 wild-type genotype (CC) and wild-type OATP1C1-rs1515777 allele containing the genotypes (AA + AG) were associated with lower odds ratio of symptoms of anxiety (OR = 0.37; 95% CI: 0.14-0.96; p = 0.041 and OR = 0.30; 95% CI: 0.12-0.76; p = 0.011, respectively). Wild-type OATP1C1-rs974453 genotype (GG) was associated with higher odds ratio of symptoms of depression (OR = 2.73; 95% CI: 1.04-7.12; p = 0.041).

CONCLUSION

Allelic variants in thyroid axis genes may predict emotional outcomes of AIS.

Novel genes involved in the genetic architecture of temperament in Brahman cattle

Cattle temperament is a complex and economically relevant trait. The objective of this study was to identify genomic regions and genes associated with cattle temperament. From a Brahman cattle population of 1,370 animals evaluated for temperament traits (Exit velocity-EV, Pen Score-PS, Temperament Score-TS), two groups of temperament-contrasting animals were identified based on their EV-average values ±1/2 standard deviation (SD). To be considered in the calm group, the EV of females ranged between 0.16–1.82 m/s (n = 50) and the EV of males ranged between 0.4–1.56 m/s (n = 48). Females were classified as temperamental if their EV ranged between 3.13–7.66 m/s (n = 46) and males were classified as temperamental if their EV ranged between 3.05–10.83 m/s (n = 45). Selected animals were genotyped using a total of 139,376 SNPs (GGP-HD-150K), evaluated for their association with EV. The Genome-Wide Association analysis (GWAS) identified fourteen SNPs: rs135340276, rs134895560, rs110190635, rs42949831, rs135982573, rs109393235, rs109531929, rs135087545, rs41839733, rs42486577, rs136661522, rs110882543, rs110864071, rs109722627, (P<8.1E-05), nine of them were located on intergenic regions, harboring seventeen genes, of which only ACER3, VRK2, FANCL and SLCO3A1 were considered candidate associated with bovine temperament due to their reported biological functions. Five SNPs were located at introns of the NRXN3, EXOC4, CACNG4 and SLC9A4 genes. The indicated candidate genes are implicated in a wide range of behavioural phenotypes and complex cognitive functions. The association of the fourteen SNPs on bovine temperament traits (EV, PS and TS) was evaluated; all these SNPs were significant for EV; only some were associated with PS and TS. Fourteen SNPs were associated with EV which allowed the identification of twenty-one candidate genes for Brahman temperament. From a functional point of view, the five intronic SNPs identified in this study, are candidates to address control of bovine temperament, further investigation will probe their role in expression of this trait.

Toxicological implication of prostaglandin transporter SLCO2A1 inhibition by cigarette smoke in exacerbation of lung inflammation

We reported that bleomycin (BLM)-induced pulmonary fibrosis was exacerbated in the prostaglandin transporter gene (Slco2a1)-deficient mice (Slco2a1(-/-)). Because cigarette smoke (CS) contributes to creating a profibrotic milieu in the respiratory region, the present study aimed to investigate the impact of CS on SLCO2A1-associated pathogenesis in the lungs of BLM-instilled mice. Bronchoalveolar lavage (BAL) fluid cell analysis indicated more severe inflammation in Slco2a1(-/-) on day 5 after BLM intratracheal instillation, and Slco2a1 deletion increased mRNA expression of pro-inflammatory cytokines (Tnf-α and Il-1β) and chemokine (Ccl5) in BAL cells. Male Slco2a1(-/-) exhibited significantly higher amounts of released Il-1β in BAL fluid, compared with female Slco2a1(-/-), male or female Slco2a1(+/+) group. The amount of PGE₂ collected in BAL fluid tended to increase in Slco2a1(-/-) compared with Slco2a1(+/+) group, whereas the PGE₂ concentrations in lung tissues were comparable between both groups. Besides, PGE₂ accumulated more in BAL fluid of male than that of female mice. Therefore, Slco2a1-deficient male mice were found to be more susceptible to BLM-treatment. Moreover, CS extracts (CSE) significantly reduced initial PGE₂ uptake by rat type1 alveolar epithelial cell-like (AT1-L) cells and human SLCO2A1-transfected cells. Exposure of AT1-L cells to CSE resulted in decreased mRNA expression of Slco2a1, suggesting that CS modulates SLCO2A1 function. These results indicate that exacerbated lung inflammation is attributed to an increase in Il-1β peptide and PGE₂ accumulation in the alveolar space, which exhibits a male predominance. SLCO2A1 inhibition by CSE is considered to be a new rationale for the lung toxicity of CS.

[Analysis of genetic variant in a child with concomitant spinal muscular atrophy and Citrin protein deficiency]

OBJECTIVE

To explore the genetic basis for a child with concomitant spinal muscular atrophy (SMA) and Citrin protein deficiency.

METHODS

The child was subjected to whole exome sequencing by using target sequence capture high-throughput sequencing. Candidate variants were verified by Sanger sequencing. The SMN genes of the patient were also analyzed through multiplex ligation-dependent probe amplification (MLPA).

RESULTS

The patient was found to carry homozygous deletion of exons 7 and 8 of the SMN1 gene, for which his parents were both carriers. The patient also carried compound heterozygous variants c.1737G>A and IVS16ins3kbof the SLA25A13 gene, in addition with compound heterozygous variants c.948G>A and c.2693T>C of the POLG gene, for which his parents were carriers, too.

CONCLUSION

Variants of the SLC25A13 gene probably underlay the deficiency of Citrin protein, which may lead to neonatal intrahepatic cholestasis (NICCD). The patient also had SMA. The compound heterozygous variants c.948G>A and c.2693T>C of the POLG gene are likely to cause mitochondrial DNA deletion syndrome type 4A, though other types of mitochondrial disease cannot be excluded.

Vectorial transport of the arginine derivatives asymmetric dimethylarginine (ADMA) and L-homoarginine by OATP4C1 and P-glycoprotein studied in double-transfected MDCK cells

Elevated plasma concentrations of the uremic toxin asymmetric dimethylarginine (ADMA) and low plasma concentrations of l-homoarginine are independently associated with cardiovascular events and mortality. Key enzymes involved in the homeostasis of both arginine derivatives are expressed in proximal tubule cells of the kidney. To get access to these enzymes, transport proteins are important. One of the transporters mediating the transport of ADMA and l-homoarginine is the solute carrier superfamily (SLC) member OATP4C1, located in the basolateral membrane of proximal tubule cells. To gain insights into the role of export pumps in the transport of both substances, we established a double-transfected MDCK cell line expressing OATP4C1 and the export pump P-glycoprotein (P-gp). Using MDCK cell monolayers, we demonstrated in time-dependent and concentration-dependent vectorial transport experiments that ADMA and l-homoarginine are transported from the basolateral to the apical compartment of MDCK-OATP4C1-P-gp cells with significantly higher transport rates compared to single-transfected MDCK-OATP4C1, MDCK-P-gp and MDCK-VC (control) cells (e.g. transport ratio MDCK-OATP4C1-P-gp/MDCK-VC: for 50 µM ADMA = 2.0-fold, for 50 µM l-homoarginine  = 3.4-fold). These results indicate that both OATP4C1 and P-gp transport the arginine derivatives ADMA and l-homoarginine and are, therefore, important for the homoeostasis of both substances.

Repression of tick microRNA-133 induces organic anion transporting polypeptide expression critical for Anaplasma phagocytophilum survival in the vector and transmission to the vertebrate host

The microRNAs (miRNAs) are important regulators of gene expression. In this study, we provide evidence for the first time to show that rickettsial pathogen Anaplasma phagocytophilum infection results in the down-regulation of tick microRNA-133 (miR-133), to induce Ixodes scapularis organic anion transporting polypeptide (isoatp4056) gene expression critical for this bacterial survival in the vector and for its transmission to the vertebrate host. Transfection studies with recombinant constructs containing transcriptional fusions confirmed binding of miR-133 to isoatp4056 mRNA. Treatment with miR-133 inhibitor resulted in increased bacterial burden and isoatp4056 expression in ticks and tick cells. In contrast, treatment with miR-133 mimic or pre-mir-133 resulted in dramatic reduction in isoatp4056 expression and bacterial burden in ticks and tick cells. Moreover, treatment of ticks with pre-mir-133 affected vector-mediated A. phagocytophilum infection of murine host. These results provide novel insights to understand impact of modulation of tick miRNAs on pathogen colonization in the vector and their transmission to infect the vertebrate host.

This study provides novel evidence that shows that down-regulation of arthropod microRNA-133 leading to enhanced expression of organic anion transporting polypeptide is not only critical for rickettsial pathogen Anaplasma phagocytophilum survival in ticks but also for this bacterial transmission from vector to the vertebrate host. Understanding how pathogens manipulate vector-signaling repertoire for their benefit would lead to the development of strategies to block their transmission from vector to the vertebrate host.

Enhanced exudation of malate in the rhizosphere due to AtALMT1 overexpression in blackgram (Vigna mungo L.) confers increased aluminium tolerance

Worldwide, 50% of soil is acidic, which induces aluminium (Al) toxicity in plants, as the phyto-availability of Al³⁺ increases in acidic soil. Plants responds to Al³⁺ toxicity by exuding organic acids into the rhizosphere. The organic acid responsible for Al³⁺ stress response varies from species to species, which in the case of blackgram (Vigna mungo L.) is citrate. In blackgram, an Arabidopsis malate transporter, AtALMT1, was overexpressed with the motive of inducing enhanced exudation of malate. Transgenics were generated using cotyledon node explants through Agrobacterium tumefaciens-mediated transformation. The putative transgenics were initially screened by AtALMT1-specific genomic DNA PCR, followed by quantitative PCR. Two independent transgenic events were identified and functionally characterized in the T₃ generation. The transgenic lines, Line 1 and 2, showed better root growth, relative water content and chlorophyll content under Al³⁺ stress. Both lines also accounted for less oxidative damage, due to reduced accumulation of ROS molecules. Photosynthetic efficiency, as measured in terms of F_v /F_m , NPQ and Y(II), increased when compared to the wild type (WT). Relative expression of genes (VmSTOP1, VmALS3, VmMATE) responsible for Al³⁺ stress response in blackgram showed that overexpression of a malate transporter did not have any effect on their expression. Malate exudation increased whereas citrate exudation did not show any divergence from the WT. A pot stress assay found that the transgenics showed better adaptation to acidic soil. This report demonstrates that the overexpression of a malate transporter in a non-malate exuding species improves adaptation to Al³⁺ toxicity in acidic soil without effecting its stress response mechanism.

Janus kinase-dependent regulation of drug detoxifying protein expression by interleukin-22 in human hepatic cells

Interleukin (IL)-22 is a cytokine up-regulated in inflammatory situations and known to exert various hepatic effects. The potential impact of IL-22 towards liver drug detoxifying proteins remains nevertheless unknown, but may be important to determine owing to the well-established alterations of liver detoxification occuring during inflammation. The present study was therefore designed to analyze the effects of IL-22 towards drug metabolizing enzyme and drug transporter expression and activity in cultured human hepatic cells. Exposure of differentiated hepatoma HepaRG cells or primary human hepatocytes to 10 ng/mL IL-22 was found to repress mRNA expression of cytochrome P-450 (CYP) 1A2, CYP3A4, CYP2B6 and CYP2C9 and of the sinusoidal sodium-taurocholate co-transporting polypeptide (NTCP); such IL-22 effects were concentration-dependent for CYP3A4 (IC50 = 1.7 ng/mL), CYP2B6 (IC50 = 0.9 ng/mL) and NTCP (IC50 = 1.8 ng/mL). Activity of CYP1A2 (phenacetin O-deethylation), CYP3A4 (midazolam hydroxylation) and CYP2B6 (bupropion hydroxylation), as well as that of NTCP (taurocholate uptake) were concomitantly decreased in IL-22-treated HepaRG cells; by contrast, activity of organic anion transporter polypeptides (OATPs) (estrone-3-sulfate uptake) and of organic cation transporter (OCT) 1 (tetra-ethylammonium uptake) remained unchanged. IL-22 was next found to activate the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) 3 pathway, whose inhibition by the JAK inhibitor ruxolitinib fully prevented the IL-22-mediated CYP3A4, CYP2B6 and NTCP repression in HepaRG cells. This JAK-dependent down-regulation of hepatic drug detoxifying proteins, notably of CYPs, by IL-22 may contribute to alteration of pharmacokinetics in patients suffering from acute and chronic inflammatory diseases and may be the source of drug-drug interactions.

Structural dissection of 13-epiestrones based on the interaction with human Organic anion-transporting polypeptide, OATP2B1

Human OATP2B1 encoded by the SLCO2B1 gene is a multispecific transporter mediating the cellular uptake of large, organic molecules, including hormones, prostaglandins and bile acids. OATP2B1 is ubiquitously expressed in the human body, with highest expression levels in pharmacologically relevant barriers, like enterocytes, hepatocytes and endothelial cells of the blood-brain-barrier. In addition to its endogenous substrates, OATP2B1 also recognizes clinically applied drugs, such as statins, antivirals, antihistamines and chemotherapeutic agents and influences their pharmacokinetics. On the other hand, OATP2B1 is also overexpressed in various tumors. Considering that elevated hormone uptake by OATP2B1 results in increased cell proliferation of hormone dependent tumors (e.g. breast or prostate), inhibition of OATP2B1 can be a good strategy to inhibit the growth of these tumors. 13-epiestrones represent a potential novel strategy in the treatment of hormone dependent cancers by the suppression of local estrogen production due to the inhibition of the key enzyme of estrone metabolism, 17ß-hydroxysteroid-dehydrogenase type 1 (HSD17ß1). Recently, we have demonstrated that various phosphonated 13-epiestrones are dual inhibitors also suppressing OATP2B1 function. In order to gain better insights into the molecular determinants of OATP2B1 13-epiestrone interaction we investigated the effect of C-2 and C-4 halogen or phenylalkynyl modified epiestrones on OATP2B1 transport function. Potent inhibitors (with EC₅₀ values in the low micromolar range) as well as non-inhibitors of OATP2B1 function were identified. Based on the structure-activity relationship (SAR) of the various 13-epiestrone derivatives we could define structural elements important for OATP2B1 inhibition. Our results may help to understand the drug/inhibitor interaction profile of OATP2B1, and also may be a useful strategy to block steroid hormone entry into tumors.

Mitochondrial SLC25 Carriers: Novel Targets for Cancer Therapy

The transfer of metabolites through the mitochondrial membranes is a vital process that is highly controlled and regulated by the inner membrane. A variety of metabolites, nucleotides, and cofactors are transported across the inner mitochondrial membrane (IMM) by a superfamily of membrane transporters which are known as the mitochondrial carrier family (MCF) or the solute carrier family 25 (SLC25 protein family). In humans, the MCF has 53 members encoded by nuclear genes. Members of the SLC25 family of transporters, which is the largest group of solute carriers, are also known as mitochondrial carriers (MCs). Because MCs are nuclear-coded proteins, they must be imported into the IMM. When compared with normal cells, the mitochondria of cancer cells exhibit significantly increased transmembrane potentials and a number of their transporters are altered. SLC25 members were identified as potential biomarkers for various cancers. The objective of this review is to summarize what is currently known about the involvement of mitochondrial SLC25 carriers in associated diseases. This review suggests that the SLC25 family could be used for the development of novel points of attack for targeted cancer therapy.

Alternative Splicing of the SLCO1B1 Gene: An Exploratory Analysis of Isoform Diversity in Pediatric Liver

The hepatic influx transporter OATP1B1 (SLCO1B1) plays an important role in the disposition of endogenous substrates and drugs prescribed to children. Alternative splicing increases the diversity of protein products from > 90% of human genes and may be triggered by developmental signals. As concentrations of several endogenous OATP1B1 substrates change during growth and development, with this exploratory study we investigated age-dependent alternative splicing of SLCO1B1 mRNA in 97 postmortem livers (fetus-adolescents). Twenty-seven splice variants were detected; 10 were confirmed by additional bioinformatic analyses and verified by quantitative polymerase chain reaction, and selected for detailed analysis based on relative abundance, association with age, and overlap with an adjacent gene. Two splice variants code for reference OATP1B1 protein, and eight code for truncated proteins. The expression of eight isoforms was associated with age. We conclude that alternative splicing of SLCO1B1 occurs frequently in children; although the functional consequences remain unknown, the data raise the possibility of a regulatory role for alternative splicing in mediating developmental changes in drug disposition.

A population-specific low-frequency variant of SLC22A12 (p.W258*) explains nearby genome-wide association signals for serum uric acid concentrations among Koreans

Prolonged hyperuricemia is a cause of gout and an independent risk factor for chronic health conditions including diabetes and chronic kidney diseases. Genome-wide association studies (GWASs) for serum uric acid (SUA) concentrations have repeatedly confirmed genetic loci including those encoding uric acid transporters such as ABCG2 and SLC9A2. However, many single nucleotide polymorphisms (SNPs) found in GWASs have been common variants with small effects and unknown functions. In addition, there is still much heritability to be explained. To identify the causative genetic variants for SUA concentrations in Korean subjects, we conducted a GWAS (1902 males) and validation study (2912 males and females) and found four genetic loci reaching genome-wide significance on chromosomes 4 (ABCG2) and 11 (FRMD8, EIF1AD and SLC22A12-NRXN2). Three loci on chromosome 11 were distributed within a distance of 1.3 megabases and they were in weak or moderate linkage disequilibrium (LD) states (r² = 0.02–0.68). In a subsequent association analysis on the GWAS loci of chromosome 11 using closely positioned markers derived from whole genome sequencing data, the most significant variant to be linked with the nearby GWAS signal was rs121907892 (c.774G>A, p.W258*) of the SLC22A12 gene. This variant, and each of the three GWAS SNPs, were in LD (r² = 0.06–0.32). The strength of association of SNPs with SUA concentration (negative logarithm of P-values) and the genetic distance (r² of LD) between rs121907892 and the surrounding SNPs showed a quantitative correlation. This variant has been found only in Korean and Japanese subjects and is known to lower the SUA concentration in the general population. Thus, this low-frequency variant, rs121907892, known to regulate SUA concentrations in previous studies, is responsible for the nearby GWAS signals.

An exclusion mechanism is epistatic to an internal detoxification mechanism in aluminum resistance in Arabidopsis

BACKGROUND

In Arabidopsis, the aluminum (Al) exclusion mechanism is mainly facilitated by ALMT1-mediated malate exudation and MATE-mediated citrate releases from the root. Recently, we have demonstrated that coordinated functioning between an ALMT1-mediated Al exclusion mechanism, via exudation of malate from the root tip, and a NIP1;2-facilitated internal detoxification mechanism, via removal of Al from the root cell wall and subsequent root-to-shoot Al translocation, plays critical roles in achieving overall Al resistance. However, the genetic relationship between ALMT1 and NIP1;2 in these processes remained unclear.

RESULTS

Through genetic and physiological analyses, we demonstrate that unlike ALMT1 and MATE, which function independently and additively, ALMT1 and NIP1;2 show an epistatic relationship in Al resistance. These results indicate that ALMT1 and NIP1;2 function in the same biochemical pathway, whereas ALMT1 and MATE in different ones.

CONCLUSION

The establishment of the epistatic relationship and the coordinated functioning between the ALMT1 and NIP1;2-mediated exclusion and internal detoxification mechanisms are pivotal for achieving overall Al resistance in the non-accumulating Arabidopsis plant. We discuss and emphasize the indispensable roles of the root cell wall for the implementation of the Al exclusion mechanism and for the establishment of an epistatic relationship between the ALMT1-mediated exclusion mechanism and the NIP1;2-facilitated internal detoxification mechanism.

Microcystin-LR Does Not Alter Cell Survival and Intracellular Signaling in Human Bronchial Epithelial Cells

Changes in ecological and environmental factors lead to an increased occurrence of cyanobacterial water blooms, while secondary metabolites-producing cyanobacteria pose a threat to both environmental and human health. Apart from oral and dermal exposure, humans may be exposed via inhalation and/or swallowing of contaminated water and aerosols. Although many studies deal with liver toxicity, less information about the effects in the respiratory system is available. We investigated the effects of a prevalent cyanotoxin, microcystin-LR (MC-LR), using respiratory system-relevant human bronchial epithelial (HBE) cells. The expression of specific organic-anion-transporting polypeptides was evaluated, and the western blot analysis revealed the formation and accumulation of MC-LR protein adducts in exposed cells. However, MC-LR up to 20 μM neither caused significant cytotoxic effects according to multiple viability endpoints after 48-h exposure, nor reduced impedance (cell layer integrity) over 96 h. Time-dependent increase of putative MC-LR adducts with protein phosphatases was not associated with activation of mitogen-activated protein kinases ERK1/2 and p38 during 48-h exposure in HBE cells. Future studies addressing human health risks associated with inhalation of toxic cyanobacteria and cyanotoxins should focus on complex environmental samples of cyanobacterial blooms and alterations of additional non-cytotoxic endpoints while adopting more advanced in vitro models.

Characteristic Facial Appearance Was the Key to Diagnosing Chronic Enteropathy Associated with SLCO2A1-associated Primary Hypertrophic Osteoarthropathy

Patients with chronic enteropathy associated with SLCO2A1 (CEAS) develop multiple circular, longitudinal, or eccentric ulcers in the ileum. It is sometimes difficult to distinguish CEAS from Crohn's disease. CEAS and primary hypertrophic osteoarthropathy (PHO) are together known to be caused by a mutation of SLCO2A1 gene. The case of a 65-year-old man whose characteristic appearance due to pachydermia of the forehead folds led to the diagnosis of CEAS with PHO is presented.

Refining genome-wide associated loci for serum uric acid in individuals with African ancestry

OBJECTIVE

Serum uric acid is the end-product of purine metabolism and at high levels is a risk factor for several human diseases including gout and cardiovascular disease. Heritability estimates range from 0.32 to 0.63. Genome-wide association studies (GWAS) provide an unbiased approach to identify loci influencing serum uric acid. Here, we performed the first GWAS for serum uric acid in continental Africans, with replication in African Americans.

METHODS

Africans (n = 4126) and African Americans (n = 5007) were genotyped on high-density GWAS arrays. Efficient mixed model association, a variance component approach, was used to perform association testing for a total of ~ 18 million autosomal genotyped and imputed variants. CAVIARBF was used to fine map significant regions.

RESULTS

We identified two genome-wide significant loci: 4p16.1 (SLC2A9) and 11q13.1 (SLC22A12). At SLC2A9, the most strongly associated SNP was rs7683856 (P = 1.60 × 10-44). Conditional analysis revealed a second signal indexed by rs6838021 (P = 5.75 × 10-17). Gene expression and regulatory motif data prioritized a single-candidate causal variant for each signal. At SLC22A12, the most strongly associated SNP was rs147647315 (P = 6.65 × 10-25). Conditional analysis and functional annotation prioritized the missense variant rs147647315 (R (Arg) > H (His)) as the sole causal variant. Functional annotation of these three signals implicated processes in skeletal muscle, subcutaneous adipose tissue and the kidneys, respectively.

CONCLUSIONS

This first GWAS of serum uric acid in continental Africans identified three associations at two loci, SLC2A9 and SLC22A12. The combination of weak linkage disequilibrium in Africans and functional annotation led to the identification of candidate causal SNPs for all three signals. Each candidate causal variant implicated a different cell type. Collectively, the three associations accounted for 4.3% of the variance of serum uric acid.

Chronic Enteropathy Associated with SLCO2A1 with Pachydermoperiostosis

A 49-year-old man complained of chronic palpitation and shortness of breath, which had recently become exacerbated. A blood examination indicated severe refractory anemia and hypoproteinemia. Physical examinations revealed anemia, a systolic murmur, and spoon nails. Multiple nonspecific ileal ulcers were observed. A pathological examination indicated a small granuloma with CD68-positive histiocytes. He had a deeply wrinkled forehead, chiseled face, and clubbed fingers. Radiography revealed periostosis of the fingers and long bones in the limb. He was diagnosed with pachydermoperiostosis. SLCO2A1 demonstrated a c.1807C>T homo-mutation. He was also diagnosed with SLCO2A1-associated chronic enteropathy and thus was treated with 5-aminosalicylic acid, which temporarily improved the ileal ulcers, anemia, and hypoalbuminemia.

Neural Alterations and Hyperactivity of the Hypothalamic-Pituitary-Thyroid Axis in Oatp1c1 Deficiency

Background: The thyroid hormones (THs) triiodothyronine (T3) and thyroxine (T4) are crucial regulators of brain development and function. Cell-specific transporter proteins facilitate TH uptake and efflux across the cell membrane, and insufficient TH transport causes hypothyroidism and mental retardation. Mutations in the TH transporters monocarboxylate transporter 8 (MCT8, SLC16A2) and the organic anion-transporting polypeptide 1C1 (OATP1C1, SLCO1C1) are associated with the psychomotor retardation Allan-Herndon-Dudley syndrome and juvenile neurodegeneration, respectively. Methods: To understand the mechanisms and test potential treatments for the recently discovered OATP1C1 deficiency, we established an oatp1c1 mutant (oatp1c1^-/-) zebrafish. Results:oatp1c1 is expressed in endothelial cells, neurons, and astrocytes in zebrafish. The activity of the hypothalamic-pituitary-thyroid axis and behavioral locomotor activity increased in oatp1c1^-/- larvae. Neuropathological analysis revealed structural alteration in radial glial cells and shorter neuronal axons in oatp1c1^-/- larvae and adults. Notably, oatp1c1^-/- and oatp1c1^-/-Xmct8^-/- adults exhibit an enlarged thyroid gland (goiter). Pharmacological assays showed that TH analogs, but not THs, can reduce the size and improve the color of the thyroid gland in adult mutant zebrafish. Conclusion: These results establish a vertebrate model for OATP1C1 deficiency that demonstrates endocrinological, neurological, and behavioral alterations mimicking findings observed in an OATP1C1-deficient patient. Further, the curative effect of TH analogs in the oatp1c1^-/- zebrafish model may provide a lead toward a treatment modality in human patients.

Primary hypertrophic osteoarthropathy related gastrointestinal complication has distinctive clinical and pathological characteristics: two cases report and review of the literature

BACKGROUND

Primary hypertrophic osteoarthropathy (PHO) is a rare disease related to HPGD and SLCO2A1 gene mutation. Gastrointestinal involvement of PHO is even rarer with unknown pathogenesis. Clinical features of GI complication in PHO mimics other auto-immune based bowel entities, such as inflammatory bowel diseases and cryptogenic multifocal ulcerous stenosing enteritis (CMUSE). We aimed to analyze the clinical, genetic, radiological and pathological features of Chinese patients with PHO and determine the difference between PHO patients presenting with and without GI involvement.

METHODS

We reported two PHO cases with gastrointestinal involvement and reviewed all the studies of PHO in Chinese population published from January 1, 2000, to April 30, 2018. Clinical and genetic presentations of PHO in Chinese patients were analyzed. We compared the characteristics of those patients with gastrointestinal involvement against those without.

RESULTS

The two patients were both males with complete-form PHO for more than 10 years. GI related symptoms included diarrhea, chronic gastrointestinal hemorrhage, incomplete intestinal obstruction, anemia, and edema, which were unresponsive to etoricoxib treatment. Radiological examinations revealed segmental intestinal stenosis and thickened intestinal wall. Endoscopic findings included multiple ulcers and mucosal inflammation. Both patients had mutations of SLCO2A1 according to sequence analysis. The surgical pathology revealed chronic inflammation involving the intestinal mucosa and submucosa, similar to histological changes in CMUSE. According to the systemic review of 158 Chinese patients with PHO, 17.2% had gastrointestinal involvement, including peptic ulcer, gastric polyps, hypertrophic gastritis, and segmental intestinal stenosis. Patients with gastrointestinal involvement were more likely to have anemia (40.0% vs. 4.5%, P < 0.001), hypoalbuminemia (16.7% vs. 0.9%, P = 0.003), and myelofibrosis (19.0% vs. 0.9%, P = 0.002) than those without. Most patients with gastrointestinal complication had SLCO2A1 mutation (86.7%, 13 /15).

CONCLUSIONS

Digestive tract involvement is uncommon in patients with PHO and often presents with anemia, and hypoalbuminemia resulted from intestinal inflammation. The intestinal pathologic characteristics are distinct from Crohn's disease but similar to CMUSE. Mutations in SLCO2A1 might be the pathogenic cause of GI involvement of PHO. NSAIDs may not be effective for PHO patients with gastrointestinal complications.

Deiodinases, organic anion transporter polypeptide polymorphisms and ischemic stroke outcomes

BACKGROUND

Ischemic stroke is a major cause of premature death and chronic disability worldwide, and individual variation in functional outcome is strongly influenced by genetic factors. Neuroendocrine signaling by the hypothalamic-hypophyseal-thyroid axis is a critical regulator of post-stroke pathogenesis, suggesting that allelic variants in thyroid hormone (TH) signaling can influence stroke outcome.

AIM

To examine associations between acute ischemic stroke (AIS) outcome and allelic variants of the TH metabolizing enzymes deiodinase type 1-3 (DIO1-3) and membrane transporting organic anion polypeptide C1 (OATP1C1).

METHODS

Eligible AIS patients from Lithuania (n = 248) were genotyped for ten DIO1-3 and OATP1C1 single nucleotide polymorphisms (SNPs): DIO1 rs12095080-A/G, rs11206244-C/T, and rs2235544-A/C; DIO2 rs225014-T/C and rs225015-G/A; DIO3 rs945006-T/G; OATP1C1 rs974453-G/A, rs10444412-T/C, rs10770704-C/T, and rs1515777-A/G. Functional outcome was evaluated one year after index AIS using the modified Rankin Scale. Analyses were adjusted for important confounders, including serum free triiodothyronine.

RESULTS

After adjustment for potential confounders, the major allelic (wild-type) DIO3 genotype rs945006-TT was associated with better 1-year AIS functional outcome (odds ratio [OR] = 0.25; 95% confidence interval [CI]: 0.08-0.74; p = .013), while the wild-type OATP1C1 genotype rs10770704-CC was associated with poorer outcome (OR = 2.00, 95%CI: 1.04-3.86; p = .038).

CONCLUSION

Allelic variants in thyroid axis genes may prove useful for prognosis and treatment guidance.

The mechanism of Oatp1a5-mediated microcystin-leucine arginine entering into GnRH neurons

Microcystin-leucine arginine (MC-LR) enters into gonadotropin-releasing hormone (GnRH) neurons and induces decline of serum GnRH levels resulting in male reproductive toxicity via hypothalamic-pituitary-testis axis. The organic anion transporting polypeptide 1a5 (Oatp1a5) is a critical transporter for the uptake of MC-LR by GnRH neurons. However, the underlying molecular mechanisms of the transport process are still elusive. In this study, we found that the transmembrane domains 2, 8, and 9 played important roles in transporting function of Oatp1a5. In addition, our data demonstrated that N-linked glycosylation was involved in the transport of MC-LR by Oatp1a5. Moreover, we showed that N-linked glycosylation sites Asn483 and Asn492 were vital for the transport function of Oatp1a5. In summary, the study furthered our understanding of mechanisms that the uptake of MC-LR by GnRH neurons and laid a theoretical foundation for preventing MC-LR from injuring male reproductive health.

Urate Transporter URAT1 in Hyperuricemia: New Insights from Hyperuricemic Models

Hyperuricemia (HUA) is positively correlated with the progression of cardiovascular and metabolic diseases. Anti-HUA drugs aim to either reduce uric acid production or promote uric acid excretion. Urate transporter 1 (URAT1) is a major urate transporter involved in renal uric acid reabsorption and excretion, making it an important anti-HUA drug target. To better understand the characteristics of URAT1 under pathological conditions, the present study aims to investigate URAT1 modulation in HUA mouse and cell line models. We found that URAT1 expression increased in the kidneys of HUA mice with normal renal function, but decreased in HUA mice with kidney injury (KI-HUA). In KI-HUA mice, treatment with anti-HUA agents, febuxostat, and benzbromarone decreased uric acid levels. However, febuxostat treatment also decreased URAT1 expression, whereas benzbromarone treatment increased its expression. Based on these in vivo findings, we propose that extracellular uric acid levels in the proximal tubule epithelial cells positively regulated URAT1 expression. In high uric acid cell models, URAT1 expression increased within 2 h of uric acid stimulation in a dose-dependent manner that supported our hypothesis. Therefore, our results suggest that URAT1 expression is positively regulated by the distinct extracellular uric acid levels in different HUA models.

Diosgenyl Saponin Inducing Endoplasmic Reticulum Stress and Mitochondria-Mediated Apoptotic Pathways in Liver Cancer Cells

Diosgenin and diosgenyl saponins as the major bioactive compounds isolated from dietary fenugreek seeds, yam roots, etc. possessed strong antitumor effects. To understand their detailed antitumor mechanisms, a fluorophore-appended derivative of diosgenin [Glc/CNHphth-diosgenin (GND)] was synthesized, starting from diosgenin and glucosamine hydrochloride in overall yields of 7-12% over 7-10 steps. Co-localization of GND with organelle-specific stains, transmission electron microscopy, and relative protein analyses demonstrated that GND crossed the plasma membrane through organic anion-transporting polypeptide 1B1 and distributed in the endoplasmic reticulum (ER), lysosome, and mitochondria. In this process, GND induced ER swelling, mitochondrial damage, and autophagosome and upregulating IRE-1α to induce autophagy and apoptosis. Furthermore, autophagy inhibitor chloroquine delayed the appearance of cleaved poly(ADP-ribose) polymerase and inhibited cleaved caspase 8, which indicated that GND induced autophagy to activate caspase-8-dependent apoptosis. These observations suggested that diosgenyl saponin was a potent anticancer agent that elicited ER stress and mitochondria-mediated apoptotic pathways in liver cancer.

Novel SLCO2A1compound heterozygous mutation causing primary hypertrophic osteoarthropathy with Bartter-like hypokalemia in a Chinese family

PURPOSE

Primary hypertrophic osteoarthropathy (PHO) is an inherited disease characterized by digital clubbing, periostosis and pachydermia with defects in the degradation of prostaglandin E2 (PGE2). Mutations in SLCO2A1 gene-encoding prostaglandin transporter (PGT) resulted in PHO, autosomal recessive 2 (PHOAR2). The spectrum of mutations and variable clinical complications of PHOAR2 has been delineated. In this study, we investigated a Chinese PHO family with a manifestation of Bartter-like hypokalemia.

METHODS

Clinical manifestations were collected and genetic analyses were performed in the PHO family.

RESULTS

The 33-year-old male proband had severe hypokalemia due to potassium loss from the kidney, while his brother had mild hypokalemia. After being treated with etoricoxib, the serum potassium level of the patient increased rapidly to the normal range which corresponded with the reduction in his serum PGE2 and PE2 metabolite (PGEM) levels. A novel SLCO2A1 compound heterozygous mutation of p.I284V and p.C459R was identified in two PHO patients in this family.

CONCLUSIONS

The present findings supported that the Bartter-like hypokalemia is a new complication of PHOAR2 caused by the high level of PGE2. Etoricoxib was demonstrated to be effective for the renal hypokalemia in PHO patients.