Challenges and Solutions in Automated Tongue Diagnosis Techniques: A Review.

Tongue diagnosis is used in various traditional medicine cultures as a non-invasive method for assessing an individual's health. Tongue image analysis has the potential for assessing the metabolism and functionality of the internal organs, making it a quick method of diagnosis. As automated systems give quantitative and objective results thereby effective in facilitating diagnosis, a review was conducted to evaluate literature on current methods of tongue diagnosis. Different methods of tongue diagnosis in the literature were identified and compared. Information on automated tongue diagnosis system, such as image acquisition, color correction, segmentation, feature extraction and classification, particularly in traditional medicine were reviewed. The aim of the review was to identify effective image processing techniques to be compatible with automated system for tongue diagnosis using some easily available to all imaging device rather than a dedicated state of art acquisition systems, which may not be easily accessible to general public. All methods identified were either being researched or developed and no specific system was identified that is currently available for routine use in clinics or home monitoring for patients. The healthcare sector could benefit from access to validated and automated tongue diagnosis systems. The feasibility of a mobile enabled platform to intelligently make use of this traditional method of diagnosis should be explored. In order to provide cheap and quick preliminary diagnosis for clinical practice automation of this noninvasive traditional technique can prove to be a boon for health care sector.

Blockade of Organic Anion Transport in Humans After Treatment With the Drug Probenecid Leads to Major Metabolic Alterations in Plasma and Urine.

Probenecid is used to treat gout and hyperuricemia as well as increase plasma levels of antiviral drugs and antibiotics. In vivo, probenecid mainly inhibits the renal SLC22 organic anion transporters OAT1 (SLC22A6), OAT3 (SLC22A8), and URAT1 (SLC22A12). To understand the endogenous role of these transporters in humans, we administered probenecid to 20 healthy participants and metabolically profiled the plasma and urine before and after dosage. Hundreds of metabolites were significantly altered, indicating numerous drug-metabolite interactions. We focused on potential OAT1 substrates by identifying 97 metabolites that were significantly elevated in the plasma and decreased in the urine, indicating OAT-mediated clearance. These included signaling molecules, antioxidants, and gut microbiome products. In contrast, urate was the only metabolite significantly decreased in the plasma and elevated in the urine, consistent with an effect on renal reuptake by URAT1. Additional support comes from metabolomics analyses of our Oat1 and Oat3 knockout mice, where over 50% of the metabolites that were likely OAT substrates in humans were elevated in the serum of the mice. Fifteen of these compounds were elevated in both knockout mice, whereas six were exclusive to the Oat1 knockout and 4 to the Oat3 knockout. These may be endogenous biomarkers of OAT function. We also propose a probenecid stress test to evaluate kidney proximal tubule organic anion transport function in kidney disease. Consistent with the Remote Sensing and Signaling Theory, the profound changes in metabolite levels following probenecid treatment support the view that SLC22 transporters are hubs in the regulation of systemic human metabolism.

Molecular Properties of Drugs Handled by Kidney OATs and Liver OATPs Revealed by Chemoinformatics and Machine Learning: Implications for Kidney and Liver Disease.

In patients with liver or kidney disease, it is especially important to consider the routes of metabolism and elimination of small-molecule pharmaceuticals. Once in the blood, numerous drugs are taken up by the liver for metabolism and/or biliary elimination, or by the kidney for renal elimination. Many common drugs are organic anions. The major liver uptake transporters for organic anion drugs are organic anion transporter polypeptides (OATP1B1 or SLCO1B1; OATP1B3 or SLCO1B3), whereas in the kidney they are organic anion transporters (OAT1 or SLC22A6; OAT3 or SLC22A8). Since these particular OATPs are overwhelmingly found in the liver but not the kidney, and these OATs are overwhelmingly found in the kidney but not liver, it is possible to use chemoinformatics, machine learning (ML) and deep learning to analyze liver OATP-transported drugs versus kidney OAT-transported drugs. Our analysis of >30 quantitative physicochemical properties of OATP- and OAT-interacting drugs revealed eight properties that in combination, indicate a high propensity for interaction with "liver" transporters versus "kidney" ones based on machine learning (e.g., random forest, k-nearest neighbors) and deep-learning classification algorithms. Liver OATPs preferred drugs with greater hydrophobicity, higher complexity, and more ringed structures whereas kidney OATs preferred more polar drugs with more carboxyl groups. The results provide a strong molecular basis for tissue-specific targeting strategies, understanding drug-drug interactions as well as drug-metabolite interactions, and suggest a strategy for how drugs with comparable efficacy might be chosen in chronic liver or kidney disease (CKD) to minimize toxicity.

Coordinate regulation of systemic and kidney tryptophan metabolism by the drug transporters OAT1 and OAT3.

How organs sense circulating metabolites is a key question. Here, we show that the multispecific organic anion transporters of drugs, OAT1 (SLC22A6 or NKT) and OAT3 (SLC22A8), play a role in organ sensing. Metabolomics analyses of the serum of Oat1 and Oat3 knockout mice revealed changes in tryptophan derivatives involved in metabolism and signaling. Several of these metabolites are derived from the gut microbiome and are implicated as uremic toxins in chronic kidney disease. Direct interaction with the transporters was supported with cell-based transport assays. To assess the impact of the loss of OAT1 or OAT3 function on the kidney, an organ where these uptake transporters are highly expressed, knockout transcriptomic data were mapped onto a "metabolic task"-based computational model that evaluates over 150 cellular functions. Despite the changes of tryptophan metabolites in both knockouts, only in the Oat1 knockout were multiple tryptophan-related cellular functions increased. Thus, deprived of the ability to take up kynurenine, kynurenate, anthranilate, and N-formylanthranilate through OAT1, the kidney responds by activating its own tryptophan-related biosynthetic pathways. The results support the Remote Sensing and Signaling Theory, which describes how "drug" transporters help optimize levels of metabolites and signaling molecules by facilitating organ cross talk. Since OAT1 and OAT3 are inhibited by many drugs, the data implies potential for drug-metabolite interactions. Indeed, treatment of humans with probenecid, an OAT-inhibitor used to treat gout, elevated circulating tryptophan metabolites. Furthermore, given that regulatory agencies have recommended drugs be tested for OAT1 and OAT3 binding or transport, it follows that these metabolites can be used as endogenous biomarkers to determine if drug candidates interact with OAT1 and/or OAT3.

Association of Race and Major Adverse Cardiac Events (MACE): The Atherosclerosis Risk in Communities (ARIC) Cohort.

BACKGROUND AND AIMS: To evaluate the association of self-reported race with major adverse cardiac events (MACE) and modification of this association by paraoxonase gene (PON1, PON2, and PON3) single nucleotide polymorphisms (SNPs). METHODS: Included in this longitudinal study were 12,770 black or white participants from the Atherosclerosis Risk in Communities (ARIC) cohort who completed a baseline visit (1987-1989) with PON genotyping. Demographic, behavioral, and health information was obtained at baseline. MACE was defined as first occurrence of myocardial infarction, stroke, or CHD-related death through 2004. Cox proportional hazards regression was used to evaluate the association between race and MACE after adjustment for age, gender, and other demographic and cardiovascular risk factors such as diabetes and hypertension. Modification of the association between PON SNPs and MACE was also assessed. RESULTS: Blacks comprised 24.6% of the ARIC cohort; overall, 14.0% of participants developed MACE. Compared with whites, blacks had 1.24 times greater hazard of MACE (OR = 1.24,95%CI = 1.10,1.39) than whites after adjusting for age, gender, BMI, cigarette and alcohol use, educational and marital status, and aspirin use. This association became nonsignificant after further adjustment for high cholesterol, diabetes, and hypertension. None of the evaluated SNPs met the significance level (p < 0.001) after Bonferroni correction for multiple comparisons. CONCLUSIONS: No association between race and MACE was identified after adjusting for high cholesterol, diabetes, and hypertension, suggesting that comorbidities are major determinants of MACE; medical intervention with focus on lifestyle and health management could ameliorate the development of MACE. Further studies are needed to confirm this observation.

The Systems Biology of Drug Metabolizing Enzymes and Transporters: Relevance to Quantitative Systems Pharmacology.

Quantitative systems pharmacology (QSP) has emerged as a transformative science in drug discovery and development. It is now time to fully rethink the biological functions of drug metabolizing enzymes (DMEs) and transporters within the framework of QSP models. The large set of DME and transporter genes are generally considered from the perspective of the absorption, distribution, metabolism, and excretion (ADME) of drugs. However, there is a growing amount of data on the endogenous physiology of DMEs and transporters. Recent studies-including systems biology analyses of "omics" data as well as metabolomics studies-indicate that these enzymes and transporters, which are often among the most highly expressed genes in tissues like liver, kidney, and intestine, have coordinated roles in fundamental biological processes. Multispecific DMEs and transporters work together with oligospecific and monospecific ADME proteins in a large multiorgan remote sensing and signaling network. We use the Remote Sensing and Signaling Theory (RSST) to examine the roles of DMEs and transporters in intratissue, interorgan, and interorganismal communication via metabolites and signaling molecules. This RSST-based view is applicable to bile acids, uric acid, eicosanoids, fatty acids, uremic toxins, and gut microbiome products, among other small organic molecules of physiological interest. Rooting this broader perspective of DMEs and transporters within QSP may facilitate an improved understanding of fundamental biology, physiologically based pharmacokinetics, and the prediction of drug toxicities based upon the interplay of these ADME proteins with key pathways in metabolism and signaling. The RSST-based view should also enable more tailored pharmacotherapy in the setting of kidney disease, liver disease, metabolic syndrome, and diabetes. We further discuss the pharmaceutical and regulatory implications of this revised view through the lens of systems physiology.

Outpatient Pharmacy Prescriptions During the First Year Following Serious Combat Injury: A Retrospective Analysis.

INTRODUCTION: Limited research has analyzed the full range of outpatient medication prescription activity following serious combat injury. The objectives of this study were to describe (1) outpatient medication prescriptions and refills during the first 12 months after serious combat injury, (2) longitudinal changes in medication prescriptions during the first-year postinjury, and (3) patient characteristics associated with outpatient prescriptions. MATERIALS AND METHODS: This was a retrospective analysis of existing health and pharmacy data for a random sample of U.S. service members who sustained serious combat injuries in the Iraq and Afghanistan conflicts, 2010-2013 (n = 381). Serious injury was defined by an Injury Severity Score (ISS) of 9 or greater. These patients typically participate in military rehabilitation programs (eg, amputation care) where prescription medications are essential. Data sources were the Expeditionary Medical Encounter Database for injury-specific data, the Pharmacy Data Transaction Service for outpatient medication prescriptions and refills, and the Military Health System Data Repository for diagnostic codes of pain and psychological disorders. Military trauma nurses reviewed casualty records to identify types of injuries. Using the American Hospital Formulary Service Pharmacologic-Therapeutic Classification system, clinicians identified 13 categories of prescription medications (eg, opioid, psychotherapeutic, immunologic) for analysis. Multivariable negative binomial and logistic regression analyses evaluated significant associations between independent variables (eg, blast injury, traumatic brain injury [TBI], ISS, limb amputation, diagnoses of chronic pain, or psychological disorders) and prescription measures (ie, number or category of medication prescriptions). We also describe longitudinal changes in prescription activity postinjury across consecutive quarterly intervals (91 days) during the first-year postinjury. RESULTS: During the first-year postinjury, patients averaged 61 outpatient prescriptions, including all initial prescriptions and refills. They averaged eight different categories of medications, primarily opioid, immunologic, gastrointestinal/genitourinary, central nervous system (CNS), nonopioid analgesic, and psychotherapeutic medications (representing 82% of prescriptions) during the first year. Prescription activity generally declined across quarters. There was still substantial prescription activity during the fourth quarter, as 79% of patients had at least one prescription. From 39 to 49% of patients had fourth-quarter prescriptions for opioid, CNS, or psychotherapeutic medications. Longitudinally, we found that 24-34% of patients had an opioid, CNS, or psychotherapeutic prescription during each of the final three quarters. In multivariable analysis, ISS, limb amputation (particularly bilateral amputation), and diagnoses of chronic pain and post-traumatic stress disorder (PTSD) were associated with significantly higher counts of individual and multiple medication prescriptions. TBI was associated with significantly lower numbers of prescriptions for certain medications. CONCLUSIONS: This is one of the first studies to provide a systematic analysis of outpatient medication prescriptions following serious combat injury. The results indicate substantial prescription activity from multiple medication categories throughout the first-year postinjury. Diagnoses of chronic pain, PTSD, and limb amputation and ISS were associated with significantly higher counts of prescriptions overall and more prescription medication categories. This study provides initial evidence to better understand medication prescription activity following serious combat injury. The results inform future research on medication prescription practices and planning for rehabilitation.

Unique metabolite preferences of the drug transporters OAT1 and OAT3 analyzed by machine learning.

The multispecific organic anion transporters, OAT1 (SLC22A6) and OAT3 (SLC22A8), the main kidney elimination pathways for many common drugs, are often considered to have largely-redundant roles. However, whereas examination of metabolomics data from Oat-knockout mice (Oat1 and Oat3KO) revealed considerable overlap, over a hundred metabolites were increased in the plasma of one or the other of these knockout mice. Many of these relatively unique metabolites are components of distinct biochemical and signaling pathways, including those involving amino acids, lipids, bile acids, and uremic toxins. Cheminformatics, together with a "logical" statistical and machine learning-based approach, identified a number of molecular features distinguishing these unique endogenous substrates. Compared with OAT1, OAT3 tends to interact with more complex substrates possessing more rings and chiral centers. An independent "brute force" approach, analyzing all possible combinations of molecular features, supported the logical approach. Together, the results suggest the potential molecular basis by which OAT1 and OAT3 modulate distinct metabolic and signaling pathways in vivo As suggested by the Remote Sensing and Signaling Theory, the analysis provides a potential mechanism by which "multispecific" kidney proximal tubule transporters exert distinct physiological effects. Furthermore, a strong metabolite-based machine-learning classifier was able to successfully predict unique OAT1 versus OAT3 drugs; this suggests the feasibility of drug design based on knockout metabolomics of drug transporters. The approach can be applied to other SLC and ATP-binding cassette drug transporters to define their nonredundant physiological roles and for analyzing the potential impact of drug-metabolite interactions.

Clinic Use at the Departments of Defense and Veterans Affairs Following Combat Related Amputations.

INTRODUCTION: Little population-based research has described the transition from Department of Defense (DoD) to Department of Veterans Affairs (VA) healthcare following combat related amputations. The objectives were to describe (1) to what extent patients used either DoD only facilities, both DoD and VA facilities, or VA only facilities during the first 5 years postinjury, (2) which specific clinics were used and (3) clinic use among patients with different levels of amputation (upper versus lower), and among patients with early or late amputation. MATERIALS AND METHODS: This was a retrospective analysis of health data extracted from the expeditionary medical encounter database (EMED) and national DoD and VA databases. Patients were 649 US service members who sustained a single major limb amputation following injuries in the Iraq and Afghanistan conflicts, 2001-2008. We compared yearly DoD and VA clinic use by patient groups with different levels of amputation (upper limb: above versus below elbow or lower limb: above versus below knee), different timing of amputation (early: within 90 days postinjury versus late: more than 90 days postinjury), military component (Active Duty versus National Guard/Reserve) and race (White versus Black). For all groups, we calculated the percentage of patients using: (1) DoD only, (2) both DoD and VA or 3) VA only clinics during each of postinjury years 1 through 5. We also calculated the percentage of patients who used specific clinics (e.g., social work, prosthetics, mental health) during each postinjury year. RESULTS: During postinjury year 1, over 98% of patients used DoD only or both DoD and VA clinics. Most individuals (70% to 78%) used both DoD and VA clinics during postinjury year 1. Use of VA only clinics increased gradually between postinjury year 2 (15% to 30% of patient groups) and year 5 (75% to 88%). This gradual transition to use of VA only clinics was seen consistently across patient groups with different anatomical levels or timing of amputation, military component or race. Patients with lower levels of amputation (versus higher levels) and individuals with early amputations (versus late) transitioned earlier to VA only care. Overall, clinic use was high as 91% to 100% of all patient groups used one or more clinics (DoD or VA) during each of the first 5 years. For specific clinics, most patients used DoD facilities related to rehabilitation (physical therapy, prosthetics) or transitional care (social work) particularly during postinjury year 1. Use of most VA clinics studied (social work, primary care, prosthetics, mental health) showed a modest increase primarily after postinjury year 1 and remained stable through postinjury year 5. The results indicated apparent underuse of psychiatric/mental health and prosthetics between postinjury year 1 and 2. CONCLUSIONS: The present study indicated a gradual transition from DoD to VA only healthcare which extended across 5 years following combat related amputations. Patients with lower levels of amputation or early amputation generally transitioned earlier to VA only healthcare. These results can inform medical planning to support a timely and clinically effective transition from DoD to VA healthcare.

Retrospective study of cardiovascular disease risk factors among a cohort of combat veterans with lower limb amputation.

INTRODUCTION: Previous studies have shown that veterans with lower limb amputation have a higher risk for cardiovascular disease (CVD) compared with population-based controls. American veterans who have served in Iraq and Afghanistan with lower limb amputation may be at a similarly higher risk. PATIENTS AND METHODS: The Navel Health Research Center (NHRC) maintains the Expeditionary Medical Encounter Database (EMED) of military personnel who have sustained combat limb amputation or serious limb injury during the conflicts in Iraq and Afghanistan. Department of Veterans Affairs data from 2003 to April 2015 was used to analyze CVD risk factors in this cohort. Veterans with either unilateral (n=442) or bilateral (n=146) lower limb amputation were compared to those with serious lower limb trauma without amputation (n=184). Multivariate regression was used to measure associations between lower limb amputation and CVD risk factors over an average of 8 years of follow-up. Outcomes included mean arterial pressure (MAP), low-density lipoprotein, high-density lipoprotein (HDL), and serum triglycerides (TG). RESULTS: Compared with the limb injury group, those with unilateral lower limb amputation had significantly lower HDL (p<0.05) and higher TG (p<0.05). Those with bilateral lower limb amputation had significantly higher MAP (p<0.05), lower HDL (p<0.01), and higher TG (p<0.001). The prevalence of metabolic syndrome, defined as type 2 diabetes or a constellation of blood pressure and lipid changes consistent with metabolic syndrome, was 8.7%, 14.9%, and 21.9% for limb injury, unilateral amputation, and bilateral amputation groups, respectively. Veterans with bilateral lower limb amputation had a 2.25-increased odds ratio (95% confidence interval 1.19-5.05) of type 2 diabetes or blood pressure and lipid changes consistent with metabolic syndrome compared to those with limb injury. CONCLUSIONS: Results suggest that veterans with lower limb amputation have a higher risk for metabolic syndrome. Primary care interventions to manage weight, blood pressure, and lipid levels are fundamental in order to reduce cardiac risk in this relatively young cohort.

A Retrospective Comparison of Five-Year Health Outcomes Following Upper Limb Amputation and Serious Upper Limb Injury in the Iraq and Afghanistan Conflicts.

BACKGROUND: Limited population-based research has described long-term health outcomes following combat-related upper limb amputation. OBJECTIVE: To compare health outcomes following upper limb amputation with outcomes following serious upper limb injury during the first 5 years postinjury. DESIGN: Retrospective cohort. SETTING: Departments of Defense (DoD) and Veterans Affairs (VA) inpatient and outpatient health care facilities. PARTICIPANTS: Three-hundred eighteen U.S. Service Members. METHODS: Patients sustained an above elbow (AE, n = 51) or below elbow (BE, n = 80) amputation or serious arm injury without amputation (NO AMP, n = 187) in the Iraq or Afghanistan conflicts, 2001 through 2008. Injuries were coded by trauma nurses. Outcomes came from DoD and VA health databases. MAIN OUTCOME MEASUREMENTS: International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) diagnostic codes. RESULTS: Most patients were injured by blast weaponry causing serious to severe injuries. All groups had a high prevalence of physical and psychological health diagnoses. The prevalence for nearly all wound complications and many physical and psychological disorders decreased substantially after postinjury year 1. The prevalence of posttraumatic stress disorder, however, increased significantly from postinjury year 1 (20%) to 3 (36%). Pain and psychological disorders ranged from 69% to 90% of patients during postinjury year 1 and remained relatively high even postinjury during year 5 (37%-53%). After adjusting for covariates, the AE group had significantly higher odds for some physical and psychological diagnoses (eg, deep vein thrombosis/pulmonary embolism, cervical pain, osteoarthritis, obesity, and mood and adjustment disorders) relative to the BE or NO AMP groups. BE patients had significantly lower odds for osteomyelitis, and AE and BE patients had lower odds for fracture nonunion and joint disorders versus NO AMP. CONCLUSIONS: The results identify similarities and differences in clinical outcomes following combat-related upper limb amputation versus serious arm injury and can inform medical planning to improve rehabilitation programs and outcomes for these patients. LEVEL OF EVIDENCE: III.

The systems biology of uric acid transporters: the role of remote sensing and signaling.

PURPOSE OF REVIEW: Uric acid homeostasis in the body is mediated by a number of SLC and ABC transporters in the kidney and intestine, including several multispecific 'drug' transporters (e.g., OAT1, OAT3, and ABCG2). Optimization of uric acid levels can be viewed as a 'systems biology' problem. Here, we consider uric acid transporters from a systems physiology perspective using the framework of the 'Remote Sensing and Signaling Hypothesis.' This hypothesis explains how SLC and ABC 'drug' and other transporters mediate interorgan and interorganismal communication (e.g., gut microbiome and host) via small molecules (e.g., metabolites, antioxidants signaling molecules) through transporters expressed in tissues lining body fluid compartments (e.g., blood, urine, cerebrospinal fluid). RECENT FINDINGS: The list of uric acid transporters includes: SLC2A9, ABCG2, URAT1 (SLC22A12), OAT1 (SLC22A6), OAT3 (SLC22A8), OAT4 (SLC22A11), OAT10 (SLC22A13), NPT1 (SLC17A1), NPT4 (SLC17A3), MRP2 (ABCC2), MRP4 (ABCC4). Normally, SLC2A9, - along with URAT1, OAT1 and OAT3, - appear to be the main transporters regulating renal urate handling, while ABCG2 appears to regulate intestinal transport. In chronic kidney disease (CKD), intestinal ABCG2 becomes much more important, suggesting remote organ communication between the injured kidney and the intestine. SUMMARY: The remote sensing and signaling hypothesis provides a useful systems-level framework for understanding the complex interplay of uric acid transporters expressed in different tissues involved in optimizing uric acid levels under normal and diseased (e.g., CKD, gut microflora dysbiosis) conditions.

Correction: A Comparison of Four-Year Health Outcomes following Combat Amputation and Limb Salvage.

[This corrects the article DOI: 10.1371/journal.pone.0170569.].

A Comparison of Four-Year Health Outcomes following Combat Amputation and Limb Salvage.

Little research has described the long-term health outcomes of patients who had combat-related amputations or leg-threatening injuries. We conducted retrospective analysis of Department of Defense and Department of Veterans Affairs health data for lower extremity combat-injured patients with (1) unilateral amputation within 90 days postinjury (early amputation, n = 440), (2) unilateral amputation more than 90 days postinjury (late amputation, n = 78), or (3) leg-threatening injuries without amputation (limb salvage, n = 107). Patient medical records were analyzed for four years postinjury. After adjusting for group differences, early amputation was generally associated with a lower or similar prevalence for adverse physical and psychological diagnoses (e.g., pain, osteoarthritis, posttraumatic stress disorder) versus late amputation and/or limb salvage. By contrast, early amputation was associated with an increased likelihood of osteoporosis during the first year postinjury. The prevalence of posttraumatic stress disorder increased for all patient groups over four years postinjury, particularly in the second year. The different clinical outcomes among combat extremity injured patients treated with early amputation, late amputation, or limb salvage highlight their different healthcare requirements. These findings can inform and optimize the specific treatment pathways that address the physical and psychological healthcare needs of such patients over time.

An Organic Anion Transporter 1 (OAT1)-centered Metabolic Network.

There has been a recent interest in the broader physiological importance of multispecific "drug" transporters of the SLC and ABC transporter families. Here, a novel multi-tiered systems biology approach was used to predict metabolites and signaling molecules potentially affected by the in vivo deletion of organic anion transporter 1 (Oat1, Slc22a6, originally NKT), a major kidney-expressed drug transporter. Validation of some predictions in wet-lab assays, together with re-evaluation of existing transport and knock-out metabolomics data, generated an experimentally validated, confidence ranked set of OAT1-interacting endogenous compounds enabling construction of an "OAT1-centered metabolic interaction network." Pathway and enrichment analysis indicated an important role for OAT1 in metabolism involving: the TCA cycle, tryptophan and other amino acids, fatty acids, prostaglandins, cyclic nucleotides, odorants, polyamines, and vitamins. The partly validated reconstructed network is also consistent with a major role for OAT1 in modulating metabolic and signaling pathways involving uric acid, gut microbiome products, and so-called uremic toxins accumulating in chronic kidney disease. Together, the findings are compatible with the hypothesized role of drug transporters in remote inter-organ and inter-organismal communication: The Remote Sensing and Signaling Hypothesis (Nigam, S. K. (2015) Nat. Rev. Drug Disc. 14, 29). The fact that OAT1 can affect many systemic biological pathways suggests that drug-metabolite interactions need to be considered beyond simple competition for the drug transporter itself and may explain aspects of drug-induced metabolic syndrome. Our approach should provide novel mechanistic insights into the role of OAT1 and other drug transporters implicated in metabolic diseases like gout, diabetes, and chronic kidney disease.

Analysis of ABCG2 and other urate transporters in uric acid homeostasis in chronic kidney disease: potential role of remote sensing and signaling.

BACKGROUND: In the setting of chronic kidney disease (CKD), altered extra-renal urate handling may be necessary to regulate plasma uric acid. The Remote Sensing and Signaling Hypothesis (Nigam S. What do drug transporters really do? Nat Rev Drug Discov 2015; 14: 29-44) suggests that multispecific solute carrier (SLC) and ATP-binding cassette (ABC) drug transporters in different tissues are part of an inter-organ communication system that maintains levels of urate and other metabolites after organ injury. METHODS: Data from the Chronic Renal Insufficiency Cohort (CRIC; n = 3598) were used to study associations between serum uric acid and single nucleotide polymorphisms (SNPs) on the following uric acid transporters: ABCG2 (BRCP), SLC22A6 (OAT1), SLC22A8 (OAT3), SLC22A10 (OAT5), SLC22A11 (OAT4), SLC22A12 (URAT1), SLC22A13 (OAT10), SLC17A1-A3 (NPTs), SLC2A9 (GLUT9), ABCC2 (MRP2) and ABCC4 (MRP4). Regression models, controlling for principal components age, gender and renal function, were run separately for those of European (EA) and African ancestry (AA), and P-values corrected for multiple comparisons. A twin cohort with participants of EA and normal renal function was used for comparison. RESULTS: Among those of EA in CRIC, statistically significant signals were observed for SNPs in ABCG2 (rs4148157; beta-coefficient = 0.68; P = 4.78E-13) and SNPs in SLC2A9 (rs13125646; beta-coefficient = -0.30; P = 1.06E-5). Among those of AA, the strongest (but not statistically significant) signals were observed for SNPs in SLC2A9, followed by SNPs in ABCG2. In the twin study (normal renal function), only SNPs in SLC2A9 were significant (rs4481233; beta-coefficient=-0.45; P = 7.0E-6). In CRIC, weaker associations were also found for SLC17A3 (NPT4) and gender-specific associations found for SLC22A8 (OAT3), SLC22A11 (OAT4), and ABCC4 (MRP4). CONCLUSIONS: In patients of EA with CKD (CRIC cohort), we found striking associations between uric acid and SNPs on ABCG2, a key transporter of uric acid by intestine. Compared with ABCG2, SLC2A9 played a much less significant role in this subset of patients with CKD. SNPs in other SLC (e.g. SLC22A8 or OAT3) and ABC (e.g. ABCC4 or MRP4) genes appear to make a weak gender-dependent contribution to uric acid homeostasis in CKD. As renal urate transport is affected in the setting of declining kidney function, extra-renal ABCG2 appears to play a compensatory role-a notion consistent with animal studies and the Remote Sensing and Signaling Hypothesis. Overall, the data indicate how different urate transporters become more or less important depending on renal function, ethnicity and gender. Therapies focused on enhancing ABCG2 urate handling may be helpful in the setting of CKD and hyperuricemia.

Handling of Drugs, Metabolites, and Uremic Toxins by Kidney Proximal Tubule Drug Transporters.

The proximal tubule of the kidney plays a crucial role in the renal handling of drugs (e.g., diuretics), uremic toxins (e.g., indoxyl sulfate), environmental toxins (e.g., mercury, aristolochic acid), metabolites (e.g., uric acid), dietary compounds, and signaling molecules. This process is dependent on many multispecific transporters of the solute carrier (SLC) superfamily, including organic anion transporter (OAT) and organic cation transporter (OCT) subfamilies, and the ATP-binding cassette (ABC) superfamily. We review the basic physiology of these SLC and ABC transporters, many of which are often called drug transporters. With an emphasis on OAT1 (SLC22A6), the closely related OAT3 (SLC22A8), and OCT2 (SLC22A2), we explore the implications of recent in vitro, in vivo, and clinical data pertinent to the kidney. The analysis of murine knockouts has revealed a key role for these transporters in the renal handling not only of drugs and toxins but also of gut microbiome products, as well as liver-derived phase 1 and phase 2 metabolites, including putative uremic toxins (among other molecules of metabolic and clinical importance). Functional activity of these transporters (and polymorphisms affecting it) plays a key role in drug handling and nephrotoxicity. These transporters may also play a role in remote sensing and signaling, as part of a versatile small molecule communication network operative throughout the body in normal and diseased states, such as AKI and CKD.

Association of the ADRB2 (rs2053044) polymorphism and angiotensin-converting enzyme-inhibitor blood pressure response in the African American Study of Kidney Disease and Hypertension.

AIM/OBJECTIVES/BACKGROUND: Hypertension is a risk factor for cardiovascular and kidney disease and is most prevalent in African-American adults. The renin-angiotensin-aldosterone system is integral in blood pressure regulation; angiotensin-converting enzyme inhibitors such as ramipril are first-line treatment options. As decreases in angiotensin result in catecholamine release, ß-adrenergic receptor (ADRB) polymorphisms may influence blood pressure response to ramipril. METHODS: Associations between ADRB polymorphisms and blood pressure response to ramipril were analyzed in the African American Study of Kidney Disease and Hypertension, a randomized clinical trial. A total of 336 participants were included in this analysis. Six polymorphisms were analyzed here: (a) ADRB1 rs1801252 (Ser49Gly) and rs1801253 (Gly389Arg); and (b) ADRB2 rs2053044, rs1042711, rs1042713 (Arg16Gly), and rs1042714 (Gln27Glu). Time to reach a mean arterial pressure (MAP) of 107 mmHg within the first 60 days after randomization was studied using Kaplan-Meier and Cox proportional hazards modeling for univariate and adjusted analyses. RESULTS: Genotypes at rs2053044, upstream from the ADRB2 5' untranslated region, were associated with time to reach target MAP among those randomized to the usual treatment group. Participants with the GG genotype achieved target MAP on average 12.2 days (38.1%) later than in comparison with those with the A allele (P=0.01). After adjusting for covariates, those with the AA/AG genotype had 2.09 greater odds of reaching MAP of 107 mmHg or less within 60 days of treatment in comparison with those with a GG genotype (hazard ratio=2.09, 95% confidence interval=1.21-3.60). CONCLUSION: Results suggest that ADRB2 rs2053044 genotypes may be a determinant of blood pressure response to ramipril. Additional studies are needed to clarify the effect of rs2053044 and other 5' untranslated region polymorphisms on gene expression and blood pressure response to angiotensin-converting enzyme inhibitors.

The organic anion transporter (OAT) family: a systems biology perspective.

The organic anion transporter (OAT) subfamily, which constitutes roughly half of the SLC22 (solute carrier 22) transporter family, has received a great deal of attention because of its role in handling of common drugs (antibiotics, antivirals, diuretics, nonsteroidal anti-inflammatory drugs), toxins (mercury, aristolochic acid), and nutrients (vitamins, flavonoids). Oats are expressed in many tissues, including kidney, liver, choroid plexus, olfactory mucosa, brain, retina, and placenta. Recent metabolomics and microarray data from Oat1 [Slc22a6, originally identified as NKT (novel kidney transporter)] and Oat3 (Slc22a8) knockouts, as well as systems biology studies, indicate that this pathway plays a central role in the metabolism and handling of gut microbiome metabolites as well as putative uremic toxins of kidney disease. Nuclear receptors and other transcription factors, such as Hnf4α and Hnf1α, appear to regulate the expression of certain Oats in conjunction with phase I and phase II drug metabolizing enzymes. Some Oats have a strong selectivity for particular signaling molecules, including cyclic nucleotides, conjugated sex steroids, odorants, uric acid, and prostaglandins and/or their metabolites. According to the "Remote Sensing and Signaling Hypothesis," which is elaborated in detail here, Oats may function in remote interorgan communication by regulating levels of signaling molecules and key metabolites in tissues and body fluids. Oats may also play a major role in interorganismal communication (via movement of small molecules across the intestine, placental barrier, into breast milk, and volatile odorants into the urine). The role of various Oat isoforms in systems physiology appears quite complex, and their ramifications are discussed in the context of remote sensing and signaling.

Lower-limb amputation and effect of posttraumatic stress disorder on Department of Veterans Affairs outpatient cost trends.

Department of Veterans Affairs (VA) outpatient costs were analyzed for combat Veterans injured in Iraq and Afghanistan from 2001 to 2008. Patients had serious lower-limb injuries (n = 170) or unilateral (n = 460) or bilateral (n = 153) lower-limb amputation(s). Total costs over the follow-up period (2003 to 2012) and annual costs were analyzed. Unadjusted mean costs per year in 2012 U.S. dollars were $7,200, $14,700 and $18,700 for limb injuries and unilateral and bilateral lower-limb amputation(s), respectively (p < 0.001). Multivariate modeling indicated that annual cost declined after the first year in the VA for Veterans with limb injuries (p < 0.001, repeated measures). In contrast, annual costs doubled after 3-5 years with unilateral (p < 0.001) and bilateral amputation(s) (p < 0.001). Among amputees, prosthetics comprised more than 50% of outpatient cost; unadjusted mean cost per year for prosthetics was 7-9 times higher in comparison with Veterans with limb injuries. Amputation status was associated with an adjusted 3.12-fold increase in mean prosthetic cost per year (p < 0.001, generalized linear model). In addition, posttraumatic stress disorder (PTSD) was associated with increased prosthetic cost by amputation status (p < 0.001) and increased psychiatric and pharmacy costs (both p < 0.001). Results indicate relatively high and sustained outpatient costs driven by prosthetics following amputation. Finally, PTSD affected cost for multiple domains of health, highlighting the importance of accurate diagnosis, treatment, and support for PTSD.