Protein tyrosine phosphatase receptor δ serves as the orexigenic asprosin receptor.

Asprosin is a fasting-induced glucogenic and centrally acting orexigenic hormone. The olfactory receptor Olfr734 is known to be the hepatic receptor for asprosin that mediates its effects on glucose production, but the receptor for asprosin's orexigenic function has been unclear. Here, we have identified protein tyrosine phosphatase receptor δ (Ptprd) as the orexigenic receptor for asprosin. Asprosin functions as a high-affinity Ptprd ligand in hypothalamic AgRP neurons, regulating the activity of this circuit in a cell-autonomous manner. Genetic ablation of Ptprd results in a strong loss of appetite, leanness, and an inability to respond to the orexigenic effects of asprosin. Ablation of Ptprd specifically in AgRP neurons causes resistance to diet-induced obesity. Introduction of the soluble Ptprd ligand-binding domain in the circulation of mice suppresses appetite and blood glucose levels by sequestering plasma asprosin. Identification of Ptprd as the orexigenic asprosin receptor creates a new avenue for the development of anti-obesity therapeutics.

Multi-parametric MRI of kidney disease progression for autosomal recessive polycystic kidney disease: mouse model and initial patient results.

BACKGROUND: Autosomal recessive polycystic kidney disease (ARPKD) is a rare but potentially lethal genetic disorder typically characterized by diffuse renal microcysts. Clinical trials for patients with ARPKD are not currently possible due to the absence of sensitive measures of ARPKD kidney disease progression and/or therapeutic efficacy. METHODS: In this study, animal and human magnetic resonance imaging (MRI) scanners were used to obtain quantitative kidney T1 and T2 relaxation time maps for both excised kidneys from bpk and wild-type (WT) mice as well as for a pediatric patient with ARPKD and a healthy adult volunteer. RESULTS: Mean kidney T1 and T2 relaxation times showed significant increases with age (p < 0.05) as well as significant increases in comparison to WT mice (p < 2 × 10-10). Significant or nearly significant linear correlations were observed for mean kidney T1 (p = 0.030) and T2 (p = 0.054) as a function of total kidney volume, respectively. Initial magnetic resonance fingerprinting assessments in a patient with ARPKD showed visible increases in both kidney T1 and T2 in comparison to the healthy volunteer. CONCLUSIONS: These preclinical and initial clinical MRI studies suggest that renal T1 and T2 relaxometry may provide an additional outcome measure to assess cystic kidney disease progression in patients with ARPKD. IMPACT: A major roadblock for implementing clinical trials in patients with ARPKD is the absence of sensitive measures of ARPKD kidney disease progression and/or therapeutic efficacy. A clinical need exists to develop a safe and sensitive measure for kidney disease progression, and eventually therapeutic efficacy, for patients with ARPKD. Mean kidney T1 and T2 MRI relaxation times showed significant increases with age (p < 0.05) as well as significant increases in comparison to WT mice (p < 2 ×10-10), indicating that T1 and T2 may provide sensitive assessments of cystic changes associated with progressive ARPKD kidney disease. This preclinical and initial clinical study suggests that MRI-based kidney T1 and T2 mapping could be used as a non-invasive assessment of ARPKD kidney disease progression. These non-invasive, quantitative MRI techniques could eventually be used as an outcome measure for clinical trials evaluating novel therapeutics aimed at limiting or preventing ARPKD kidney disease progression.

Targeted Radiosensitizers for MR-Guided Radiation Therapy of Prostate Cancer.

Adjuvant radiotherapy is frequently prescribed to treat cancer. To minimize radiation-related damage to healthy tissue, it requires high precision in tumor localization and radiation dose delivery. This can be achieved by MR guidance and targeted amplification of radiation dose selectively to tumors by using radiosensitizers. Here, we demonstrate prostate cancer-targeted gold nanoparticles (AuNPs) for MR-guided radiotherapy to improve the targeting precision and efficacy. By conjugating Gd(III) complexes and prostate-specific membrane antigen (PSMA) targeting ligands to AuNP surfaces, we found enhanced uptake of AuNPs by PSMA-expressing cancer cells with excellent MR contrast and radiation therapy outcome in vitro and in vivo. The AuNPs binding affinity and r1 relaxivity were dramatically improved and the combination of Au and Gd(III)provided better tumor suppression after radiation. The precise tumor localization by MR and selective tumor targeting of the PSMA-1-targeted AuNPs could enable precise radiotherapy, reduction in irradiating dose, and minimization of healthy tissue damage.

PTPmu-targeted nanoparticles label invasive pediatric and adult glioblastoma.

Poor prognosis for glioblastoma (GBM) is a consequence of the aggressive and infiltrative nature of gliomas where individual cells migrate away from the main tumor to distant sites, making complete surgical resection and treatment difficult. In this manuscript, we characterize an invasive pediatric glioma model and determine if nanoparticles linked to a peptide recognizing the GBM tumor biomarker PTPmu can specifically target both the main tumor and invasive cancer cells in adult and pediatric glioma models. Using both iron and lipid-based nanoparticles, we demonstrate by magnetic resonance imaging, optical imaging, histology, and iron quantification that PTPmu-targeted nanoparticles effectively label adult gliomas. Using PTPmu-targeted nanoparticles in a newly characterized orthotopic pediatric SJ-GBM2 model, we demonstrate individual tumor cell labeling both within the solid tumor margins and at invasive and dispersive sites.

Dynamic, Simultaneous Concentration Mapping of Multiple MRI Contrast Agents with Dual Contrast - Magnetic Resonance Fingerprinting.

Synchronous assessment of multiple MRI contrast agents in a single scanning session would provide a new "multi-color" imaging capability similar to fluorescence imaging but with high spatiotemporal resolution and unlimited imaging depth. This multi-agent MRI technology would enable a whole new class of basic science and clinical MRI experiments that simultaneously explore multiple physiologic/molecular events in vivo. Unfortunately, conventional MRI acquisition techniques are only capable of detecting and quantifying one paramagnetic MRI contrast agent at a time. Herein, the Dual Contrast - Magnetic Resonance Fingerprinting (DC-MRF) methodology was extended for in vivo application and evaluated by simultaneously and dynamically mapping the intra-tumoral concentration of two MRI contrast agents (Gd-BOPTA and Dy-DOTA-azide) in a mouse glioma model. Co-registered gadolinium and dysprosium concentration maps were generated with sub-millimeter spatial resolution and acquired dynamically with just over 2-minute temporal resolution. Mean tumor Gd and Dy concentration measurements from both single agent and dual agent DC-MRF studies demonstrated significant correlations with ex vivo mass spectrometry elemental analyses. This initial in vivo study demonstrates the potential for DC-MRF to provide a useful dual-agent MRI platform.

Imaging breast cancer using a dual-ligand nanochain particle.

Nanoparticles often only exploit the upregulation of a receptor on cancer cells to enhance intratumoral deposition of therapeutic and imaging agents. However, a single targeting moiety assumes that a tumor is homogenous and static. Tumoral microenvironments are both heterogenous and dynamic, often displaying variable spatial and temporal expression of targetable receptors throughout disease progression. Here, we evaluated the in vivo performance of an iron oxide nanoparticle in terms of targeting and imaging of orthotropic mouse models of aggressive breast tumors. The nanoparticle, a multi-component nanochain, was comprised of 3-5 iron oxide nanoparticles chemically linked in a linear chain. The nanoparticle's surface was decorated with two types of ligands each targeting two different upregulated biomarkers on the tumor endothelium, P-selectin and fibronectin. The nanochain exhibited improved tumor deposition not only through vascular targeting but also through its elongated structure. A single-ligand nanochain exhibited a ~2.5-fold higher intratumoral deposition than a spherical nanoparticle variant. Furthermore, the dual-ligand nanochain exhibited higher consistency in generating detectable MR signals compared to a single-ligand nanochain. Using a 7T MRI, the dual-ligand nanochains exhibited highly detectable MR signal within 3h after injection in two different animal models of breast cancer.

Absence of leptin signaling allows fat accretion in cystic fibrosis mice.

Negative energy balance is a prevalent feature of cystic fibrosis (CF). Pancreatic insufficiency, elevated energy expenditure, lung disease, and malnutrition, all characteristic of CF, contribute to the negative energy balance causing low body-growth phenotype. As low body weight and body mass index strongly correlate with poor lung health and survival of patients with CF, improving energy balance is an important clinical goal (e.g., high-fat diet). CF mouse models also exhibit negative energy balance (growth retardation and high energy expenditure), independent from exocrine pancreatic insufficiency, lung disease, and malnutrition. To improve energy balance through increased caloric intake and reduced energy expenditure, we disrupted leptin signaling by crossing the db/db leptin receptor allele with mice carrying the R117H Cftr mutation. Compared with db/db mice, absence of leptin signaling in CF mice (CF db/db) resulted in delayed and moderate hyperphagia with lower de novo lipogenesis and lipid deposition, producing only moderately obese CF mice. Greater body length was found in db/db mice but not in CF db/db, suggesting CF-dependent effect on bone growth. The db/db genotype resulted in lower energy expenditure regardless of Cftr genotype leading to obesity. Despite the db/db genotype, the CF genotype exhibited high respiratory quotient indicating elevated carbohydrate oxidation, thus limiting carbohydrates for lipogenesis. In summary, db/db-linked hyperphagia, elevated lipogenesis, and morbid obesity were partially suppressed by reduced CFTR activity. CF mice still accrued large amounts of adipose tissue in contrast to mice fed a high-fat diet, thus highlighting the importance of dietary carbohydrates and not simply fat for energy balance in CF. NEW & NOTEWORTHY We show that cystic fibrosis (CF) mice are able to accrue fat under conditions of carbohydrate overfeeding, increased lipogenesis, and decreased energy expenditure, although length was unaffected. High-fat diet feeding failed to improve growth in CF mice. Morbid db/db-like obesity was reduced in CF double-mutant mice by reduced CFTR activity.

A novel synthetic route for high-index faceted iron oxide concave nanocubes with high T2 relaxivity for in vivo MRI applications.

Iron oxide nanoparticles (IONPs) with high-index facets have shown great potential as high performance T2 contrast agents for MRI. Previous synthetic approaches focused mainly on ion-directed or oxidative etching methods. Herein, we report a new synthetic route for preparing high-index faceted iron oxide concave nanocubes using a bulky coordinating solvent. Through the systematic replacement of a non-coordinating solvent, 1-octadecene, with trioctylamine, the solvent interaction with the nanoparticle surface is modified, thereby, promoting the growth evolution of the IONPs from spherical to concave cubic morphology. The presence of the bulky trioctylamine solvent results in particle size increase and the formation of nanoparticles with enhanced shape anisotropy. A well-defined concave nanocube structure was evident from the early stages of particle growth, further confirming the important role of bulky coordinating solvents in nanoparticle structural development. The unique concave nanocube morphology has a direct influence on the magnetic properties of the IONPs, ultimately leading to an ultra-high T2 relaxivity (862.2 mM-1 s-1), and a 2-fold enhancement in T2*-weighted in vivo MRI contrast compared to spherical IONP analogs.

Quantitative magnetic resonance imaging assessments of autosomal recessive polycystic kidney disease progression and response to therapy in an animal model.

BackgroundAutosomal recessive polycystic kidney disease (ARPKD) is associated with significant mortality and morbidity, and currently, there are no disease-specific treatments available for ARPKD patients. One major limitation in establishing new therapies for ARPKD is a lack of sensitive measures of kidney disease progression. Magnetic resonance imaging (MRI) can provide multiple quantitative assessments of the disease.MethodsWe applied quantitative image analysis of high-resolution (noncontrast) T2-weighted MRI techniques to study cystic kidney disease progression and response to therapy in the PCK rat model of ARPKD.ResultsSerial imaging over a 2-month period demonstrated that renal cystic burden (RCB, %)=[total cyst volume (TCV)/total kidney volume (TKV) × 100], TCV, and, to a lesser extent, TKV detected cystic kidney disease progression, as well as the therapeutic effect of octreotide, a clinically available medication shown previously to slow both kidney and liver disease progression in this model. All three MRI measures correlated significantly with histologic measures of renal cystic area, although the correlation of RCB and TCV was stronger than that of TKV.ConclusionThese preclinical MRI results provide a basis for applying these quantitative MRI techniques in clinical studies, to stage and measure progression in human ARPKD kidney disease.

Improved Growth Patterns in Cystic Fibrosis Mice after Loss of Histone Deacetylase 6.

Growth failure in cystic fibrosis (CF) patients has been well-documented and shown to correlate with poorer disease outcomes. This observation is also true in CF animal models, including mouse, pig, rat, and ferret. The etiology underlying growth deficits is unknown, and our previous work demonstrated reduced tubulin acetylation in CF cell models and tissue that is correctable by inhibition of histone deacetylase-6 (HDAC6). Here, we hypothesize that loss of HDAC6 will improve growth phenotype in a CF mouse model. Hdac6 knockout mice were crossed with F508del (CF) mice to generate F508del/Hdac6 (CF/HDA) mice. Growth, fat deposits, survival, and bioelectric measurements were analyzed. CF/HDA mice displayed improvements in length and weight with no correction of CFTR function. Mechanistically, Igf1 levels likely account for increased length and improvements in fertility. Weight gain is attributed to increased fat deposits potentially mediated by increased adipocyte differentiation. CF-related growth deficits can be improved via inhibition of HDAC6, further implicating it as a potential therapeutic target for CF.

Dynamic Quantitative T1 Mapping in Orthotopic Brain Tumor Xenografts.

Human brain tumors such as glioblastomas are typically detected using conventional, nonquantitative magnetic resonance imaging (MRI) techniques, such as T2-weighted and contrast enhanced T1-weighted MRI. In this manuscript, we tested whether dynamic quantitative T1 mapping by MRI can localize orthotopic glioma tumors in an objective manner. Quantitative T1 mapping was performed by MRI over multiple time points using the conventional contrast agent Optimark. We compared signal differences to determine the gadolinium concentration in tissues over time. The T1 parametric maps made it easy to identify the regions of contrast enhancement and thus tumor location. Doubling the typical human dose of contrast agent resulted in a clearer demarcation of these tumors. Therefore, T1 mapping of brain tumors is gadolinium dose dependent and improves detection of tumors by MRI. The use of T1 maps provides a quantitative means to evaluate tumor detection by gadolinium-based contrast agents over time. This dynamic quantitative T1 mapping technique will also enable future quantitative evaluation of various targeted MRI contrast agents.

Imaging metastasis using an integrin-targeting chain-shaped nanoparticle.

While the enhanced permeability and retention effect may promote the preferential accumulation of nanoparticles into well-vascularized primary tumors, it is ineffective in the case of metastases hidden within a large population of normal cells. Due to their small size, high dispersion to organs, and low vascularization, metastatic tumors are less accessible to targeted nanoparticles. To tackle these challenges, we designed a nanoparticle for vascular targeting based on an α(v)ß(3) integrin-targeted nanochain particle composed of four iron oxide nanospheres chemically linked in a linear assembly. The chain-shaped nanoparticles enabled enhanced "sensing" of the tumor-associated remodeling of the vascular bed, offering increased likelihood of specific recognition of metastatic tumors. Compared to spherical nanoparticles, the chain-shaped nanoparticles resulted in superior targeting of α(v)ß(3) integrin due to geometrically enhanced multivalent docking. We performed multimodal in vivo imaging (fluorescence molecular tomography and magnetic resonance imaging) in a non-invasive and quantitative manner, which showed that the nanoparticles targeted metastases in the liver and lungs with high specificity in a highly aggressive breast tumor model in mice.

A heat-shock protein co-inducer treatment improves behavioral performance in rats exposed to hypoxia.

We investigated the effect of a heat-shock protein co-inducer, arimoclomol (CytRx, LA, CA), on hypoxia-adaptive responses using a rat model of simulated altitude exposure (hypobaric hypoxia).Cognitive function was measured using a T-maze and an object recognition test.Motor function was measured using an inclined-screen test and an adhesion removal test. Immunohistochemical analyses were assessed in brain for heat-shock protein 70 (HSP 70), intercellular adhesion molecule 1 (ICAM- 1) and apoptosis (TUNEL staining). Results show that both cognitive and motor performances were improved in rats treated with arimoclomol during hypoxic exposure; the hypoxia-induced expression of HSP70 and ICAM-1, and TUNEL-positive cells were reduced in brain with the treatment.Our data suggest that the arimoclomol treatment reduces the hypoxia-induced stress in brain tissue, and also improves the behavioral performance in rats during hypoxic adaptation.