Preclinical Evaluation of the Reversible Monoacylglycerol Lipase PET Tracer (R)-[11C]YH132: Application in Drug Development and Neurodegenerative Diseases

Monoacylglycerol lipase (MAGL) plays a crucial role in the degradation of 2-arachidonoylglycerol (2-AG), one of the major endocannabinoids in the brain. Inhibiting MAGL could lead to increased levels of 2-AG, which showed beneficial effects on pain management, anxiety, inflammation, and neuroprotection. In the current study, we report the characterization of an enantiomerically pure (R)-[11C]YH132 as a novel MAGL PET tracer. It demonstrates an improved pharmacokinetic profile compared to its racemate. High in vitro MAGL specificity of (R)-[11C]YH132 was confirmed by autoradiography studies using mouse and rat brain sections. In vivo, (R)-[11C]YH132 displayed a high brain penetration, and high specificity and selectivity toward MAGL by dynamic PET imaging using MAGL knockout and wild-type mice. Pretreatment with a MAGL drug candidate revealed a dose-dependent reduction of (R)-[11C]YH132 accumulation in WT mouse brains. This result validates its utility as a PET probe to assist drug development. Moreover, its potential application in neurodegenerative diseases was explored by in vitro autoradiography using brain sections from animal models of Alzheimer's disease and Parkinson's disease.

Identification of (R)-[18F]YH134 for Monoacylglycerol Lipase Neuroimaging and Exploration of Its Use for Central Nervous System and Peripheral Drug Development

This study aimed to evaluate (R)-[18F]YH134 as a novel PET tracer for imaging monoacylglycerol lipase (MAGL). Considering the ubiquitous expression of MAGL throughout the whole body, the impact of various MAGL inhibitors on (R)-[18F]YH134 brain uptake and its application in brain-periphery crosstalk were explored. Methods: MAGL knockout and wild-type mice were used to evaluate (R)-[18F]YH134 in in vitro autoradiography and PET experiments. To explore the impact of peripheral MAGL occupancy on (R)-[18F]YH134 brain uptake, PET kinetics with an arterial input function were studied in male Wistar rats under baseline and blocking conditions. Results: In in vitro autoradiography, (R)-[18F]YH134 revealed a heterogeneous distribution pattern with high binding to MAGL-rich brain regions in wild-type mouse brain slices, whereas the radioactive signal was negligible in MAGL knockout mouse brain slices. The in vivo brain PET images of (R)-[18F]YH134 in wild-type and MAGL knockout mice demonstrated its high specificity and selectivity in mouse brain. A Logan plot with plasma input function was applied to estimate the distribution volume (V T) of (R)-[18F]YH134. V T was significantly reduced by a brain-penetrant MAGL inhibitor but was unchanged by a peripherally restricted MAGL inhibitor. The MAGL target occupancy in the periphery was estimated using (R)-[18F]YH134 PET imaging data from the brain. Conclusion: (R)-[18F]YH134 is a highly specific and selective PET tracer with favorable kinetic properties for imaging MAGL in rodent brain. Our results showed that blocking of the peripheral target influences brain uptake but not the V T of (R)-[18F]YH134. (R)-[18F]YH134 can be used for estimating the dose of MAGL inhibitor at half-maximal peripheral target occupancy.

[Analysis of the incidence and symptomatology of low anterior resection syndrome after laparoscopic anterior resection for rectal cancer]

Objective: This study aims to explore the temporal trend of Low Anterior Resection Syndrome (LARS) and its symptoms after laparoscopic anterior resection for rectal cancer. Methods: A retrospective cohort study design was employed. The study included primary rectal (adenocarcinoma) cancer patients who underwent laparoscopic anterior resection at Tongji Hospital, Huazhong University of Science and Technology, between January 1, 2010, and December 31, 2020. Complete medical records and follow-up data at 3, 6, 9, 12, and 18 months postoperatively were available for all patients. A total of 1454 patients were included, of whom 1094 (75.2%) were aged ≤65 years, and 597 (41.1%) were females. Among them, 1040 cases (71.5%) had an anastomosis-to-anus distance of 0-5cm, and 86 cases (5.9%) received neoadjuvant treatment. All patients completed the Chinese version of the LARS questionnaire and their LARS occurrence and specific symptom information were recorded at 3, 6, 9, 12, and 18 months postoperatively. Considering past literature and clinical experience, further subgroup analyses were performed to explore the potential impact factors on severe LARS, including anastomosis level, preoperative neoadjuvant therapy, postoperative adjuvant therapy, and the presence of preventive stoma. Results: The occurrence rates of LARS at 3, 6, 9, 12, and 18 months postoperatively were 78.5% (1142/1454), 71.4% (1038/1454), 55.0% (799/1454), 45.7% (664/1454), and 45.7% (664/1454), respectively (χ2=546.180, P<0.001). No statistically significant difference was observed between the 12-month and 18-month time points (P>0.05). When compared with the symptoms at 3 months, the occurrence rates of gas incontinence [1.7% (24/1454) vs. 33.9% (493/1454)], liquid stool incontinence [3.9% (56/1454) vs. 41.9% (609/1454)], increased stool frequency [79.6% (1158/1454) vs. 95.9% (1395/1454)], stool clustering [74.3% (1081/1454) vs. 92.9% (1351/1454)], and stool urgency [46.5% (676/1454) vs. 78.7% (1144/1454)] in the LARS symptom spectrum were significantly alleviated at 12 months (all P<0.05) and remained stable beyond 12 months (all P>0.05). With the extension of postoperative time, the incidence rates of severe LARS exhibited a decreasing trend in different subgroups, of anastomosis level, preoperative neoadjuvant therapy, postoperative adjuvant therapy, and the presence of preventive stoma, and reached stability at 12 months postoperatively (all P>0.05). Conclusion: LARS and its specific symptom profile showed a trend of gradual improvement over time up to 1 year postoperatively, and stabilized after more than 1 year. Increased stool frequency and stool clustering are the most common features of abnormal bowel dys function, which improve slowly after surgery.

Metabotropic glutamate receptor 5 (mGluR5) is associated with neurodegeneration and amyloid deposition in Alzheimer's disease: A [18F]PSS232 PET/MRI study

BACKGROUND

Metabotropic glutamate receptor 5 (mGluR5) is involved in regulating integrative brain function and synaptic transmission. Aberrant mGluR5 signaling and relevant synaptic failure play a key role in the initial pathophysiological mechanism of Alzheimer's disease (AD). The study aims to investigate the association between mGluR5 availability and AD's biomarkers and cognitive function.

METHODS

We examined 35 individuals with mGluR5 tracer [18F]PSS232 to assess mGluR5 availability, and with [18F]Florbetapir PET to assess global amyloid deposition, and [18F]FDG PET to assess glucose metabolism. The plasma neurofilament light (NfL) and p-tau181 levels in a subset of individuals were measured (n = 27). The difference in mGluR5 availability between the AD and normal control (NC) groups was explored. The associations of mGluR5 availability with amyloid deposition, glucose metabolism, gray matter volume (GMV), neuropsychological assessment scores, and plasma biomarkers were analyzed.

RESULTS

The mGluR5 availability was significantly reduced in AD patients' hippocampus and parahippocampal gyrus compared to NCs. Global amyloid deposition was positively associated with mGluR5 availability in the AD group and reversely associated in the NC group. The mGluR5 availability was positively correlated with regional glucose metabolism in the overall and stratified analyses. The availability of mGluR5 in the hippocampus and parahippocampal gyrus demonstrated a strong relationship with the GMV of the medial temporal lobe, plasma p-tau181 or NfL levels, and global cognitive performance.

CONCLUSIONS

[18F]PSS232 PET can quantify the changes of mGluR5 availability in the progression of AD. mGluR5 availability correlated not only with neuropathological biomarkers of AD but also with neurodegenerative biomarkers and cognitive performance. mGluR5 may be a novel neurodegenerative biomarker, and whether mGluR5 could be a potential therapeutic target for AD needs to be further studied.

The impact of tau deposition and hypometabolism on cognitive impairment and longitudinal cognitive decline

INTRODUCTION

Tau and neurodegeneration strongly correlate with cognitive impairment, as compared to amyloid. However, their contribution in explaining cognition and predicting cognitive decline in memory clinics remains unclarified.

METHODS

We included 94 participants with Mini-Mental State Examination (MMSE), tau positron emission tomography (PET), amyloid PET, fluorodeoxyglucose (FDG) PET, and MRI scans from Geneva Memory Center. Linear regression and mediation analyses tested the independent and combined association between biomarkers, cognitive performance, and decline. Linear mixed-effects and Cox proportional hazards models assessed biomarkers' prognostic values.

RESULTS

Metabolism had the strongest association with cognition (r = 0.712; p < 0.001), followed by tau (r = -0.682; p < 0.001). Neocortical tau showed the strongest association with cognitive decline (r = -0.677; p < 0.001). Metabolism mediated the association between tau and cognition and marginally mediated the one with decline. Tau positivity represented the strongest risk factor for decline (hazard ratio = 32).

DISCUSSION

Tau and neurodegeneration synergistically contribute to global cognitive impairment while tau drives decline. The tau PET superior prognostic value supports its implementation in memory clinics.

HIGHLIGHTS

Hypometabolism has the strongest association with concurrent cognitive impairment. Neocortical tau pathology is the main determinant of cognitive decline over time. FDG-PET has a superior value compared to MRI as a measure of neurodegeneration. The prognostic value of tau-PET exceeded all other neuroimaging modalities.

Effects of direct-fed microbial supplementation on performance and immune parameters of lactating dairy cows

We evaluated the effects of supplementing bacterial direct-fed microbial (DFM) on performance, apparent total-tract digestibility, rumen fermentation, and immune parameters of lactating dairy cows. One hundred fourteen multiparous Holstein cows (41 ± 7 DIM) were used in a randomized complete block design with an experiment comprising 14 d of a covariate (pre-experimental sample and data collection) and 91 d of an experimental period. Cows were blocked based on energy-corrected milk (ECM) yield during the covariate period and the following treatments were randomly assigned within each block: (1) control (CON), corn silage-based total mixed ration without DFM; (2) PRO-A, basal diet top-dressed with a mixture of Lactobacillus animalis and Propionibacterium freudenreichii at 3 × 109 cfu/d; and 3) PRO-B, basal diet top-dressed with a mixture of L. animalis, P. freudenreichii, Bacillus subtilis, and Bacillus licheniformis at 11.8 × 109 cfu/d. Milk yield, dry matter intake (DMI), and body weight were measured daily, while milk samples for component analysis were taken on 2 consecutive days of each week of data collection. Feces, urine, rumen, and blood samples were taken during the covariate period, wk 4, 7, 10, and 13 for estimation of digestibility, N-partitioning, rumen fermentation, plasma nutrient status and immune parameters. Treatments had no effect on DMI and milk yield. Fat-corrected milk (3.5% FCM) and milk fat yield were improved with PRO-B, while milk fat percent and feed efficiency (ECM/DMI) tended to increase with PRO-B compared with PRO-A and CON. Crude fat digestibility was greater with PRO-B compared with CON. Feeding CON and PRO-A resulted in higher total volatile fatty acid concentration relative to PRO-B. Percentage of neutrophils tended to be reduced with PRO-A compared with CON and PRO-B. The mean fluorescence intensity (MFI) of anti-CD44 antibody on granulocytes tended to be higher in PRO-B compared with CON. The MFI of anti-CD62L antibody on CD8+ T cells was lower in PRO-A than PRO-B, with PRO-A also showing a tendency to be lower than CON. This study indicates the potential of DFM to improve fat digestibility with consequential improvement in fat corrected milk yield, feed efficiency and milk fat yield by lactating dairy cows. The study findings also indicate that dietary supplementation with DFM may augment immune parameters or activation of immune cells, including granulocytes and T cells; however, the overall effects on immune parameters are inconclusive.

Proof-of-concept optimization of a copper-mediated 18F-radiosynthesis of a novel MAGL PET tracer on a high-throughput microdroplet platform and its macroscale translation

Copper-mediated radiofluorination has demonstrated remarkable potential in forming aromatic C-18F bonds of radioligands for positron emission tomography (PET). Achieving optimal results often requires optimization efforts, requiring a substantial amount of radiolabeling precursor and time, severely limiting the experimental throughput. Recently, we successfully showcased the feasibility of performing and optimizing Cu-mediated radiosynthesis on a high-throughput microdroplet platform using the well-known and clinically used radioligand [18F]FDOPA as an illustrative example. In our current work, we optimized the Cu-mediated synthesis of a novel monoacylglycerol lipase (MAGL) PET tracer ([18F]YH149), showing the versatility of droplet-based techniques for early stage tracer development. Across 5 days, we conducted a total of 117 experiments, studying 36 distinct conditions, while utilizing <15 mg of total organoboron precursor. Compared to the original report in which the radiochemical yield (RCY) was 4.4 ± 0.5% (n = 5), the optimized droplet condition provided a substantial improvement in RCY (52 ± 8%, n = 4) and showed excellent radiochemical purity (100%) and molar activity (77-854 GBq μmol-1), using a starting activity of 0.2-1.45 GBq. Furthermore, we showed for the first time a translation of the optimized microscale conditions to a vial-based method. With similar starting activity (0.2-1.44 GBq), the translated synthesis exhibited a comparable RCY of 50 ± 10% (n = 4) while maintaining excellent radiochemical purity (100%) and acceptable molar activity (20-46 GBq μmol-1). The successful translation to vial-based reactions ensures wider applicability of the optimized synthesis by leveraging widely available commercial vial-based synthesis modules.

Reducing kidney uptake of radiolabelled exendin-4 using variants of the renally cleavable linker MVK

BACKGROUND

Peptidic radiotracers are preferentially excreted through the kidneys, which often results in high persistent renal retention of radioactivity, limiting or even preventing therapeutic clinical translation of these radiotracers. Exendin-4, which targets the glucagon-like-peptide 1 receptor (GLP-1R) overexpressed in insulinomas and in congenital hyperinsulinism, is an example thereof. The use of the tripeptide MVK, which is readily cleaved between methionine and valine by neprilysin at the renal brush border membrane, already showed promising results in reducing kidney uptake as reported in the literature. Based on our previous findings we were interested how linker variants with multiple copies of the MV-motive influence renal washout of radiolabelled exendin-4.

RESULTS

Three exendin-4 derivatives, carrying either one MVK, a MV-MVK or a MVK-MVK linker were synthesized and compared to a reference compound lacking a cleavable linker. In vivo results of a biodistribution in GLP-1R overexpressing tumour bearing mice at 24 h post-injection demonstrated a significant reduction (at least 57%) of renal retention of all 111In-labeled exendin-4 compounds equipped with a cleavable linker compared to the reference compound. While the insertion of the single linker MVK led to a reduction in kidney uptake of 70%, the dual approach with the linker MV-MVK slightly, but not significantly enhanced this effect, with 77% reduction in kidney uptake compared to the reference. In vitro IC50 and cell uptake studies were conducted and demonstrated that though the cleavable linkers negatively influenced the affinity towards the GLP-1R, cell uptake remained largely unaffected, except for the MV-MVK cleavable linker conjugate, which displayed lower cell uptake than the other compounds. Importantly, the tumour uptake in the biodistribution study was not significantly affected with 2.9, 2.5, 3.2 and 1.5% iA/g for radiolabelled Ex4, MVK-Ex4, MV-MVK-Ex4 and MVK-MVK-Ex4, respectively.

CONCLUSION

Cleavable linkers are highly efficient in reducing the radioactivity burden in the kidney. Though the dual linker approach using the instillation of MV-MVK or MVK-MVK between exendin-4 and the radiometal chelator did not significantly outperform the single cleavable linker MVK, further structural optimization or the combination of different cleavable linkers could be a stepping stone in reducing radiation-induced nephrotoxicity.

Imaging increased metabolism in the spinal cord in mice after middle cerebral artery occlusion

Emerging evidence indicates crosstalk between the brain and hematopoietic system following cerebral ischemia. Here, we investigated metabolism and oxygenation in the spleen and spinal cord in a transient middle cerebral artery occlusion (tMCAO) model. Sham-operated and tMCAO mice underwent [18F]fluorodeoxyglucose (FDG)-positron emission tomography (PET) to assess glucose metabolism. Naïve, sham-operated and tMCAO mice underwent multispectral optoacoustic tomography (MSOT) assisted by quantitative model-based reconstruction and unmixing algorithms for accurate mapping of oxygenation patterns in peripheral tissues at 24 h after reperfusion. We found increased [18F]FDG uptake and reduced MSOT oxygen saturation, indicating hypoxia in the thoracic spinal cord of tMCAO mice compared with sham-operated mice but not in the spleen. Reduced spleen size was observed in tMCAO mice compared with sham-operated mice ex vivo. tMCAO led to an increase in the numbers of mature T cells in femoral bone marrow tissues, concomitant with a stark reduction in these cell subsets in the spleen and peripheral blood. The combination of quantitative PET and MSOT thus enabled observation of hypoxia and increased metabolic activity in the spinal cord of tMCAO mice at 24 h after occlusion compared to sham-operated mice.

ATN profile classification across two independent prospective cohorts

BACKGROUND

The ATN model represents a research framework used to describe in subjects the presence or absence of Alzheimer's disease (AD) pathology through biomarkers. The aim of this study was to describe the prevalence of different ATN profiles using quantitative imaging biomarkers in two independent cohorts, and to evaluate the pertinence of ATN biomarkers to identify comparable populations across independent cohorts.

METHODS

A total of 172 subjects from the Geneva Memory Clinic and 113 volunteers from a study on healthy aging at the University Hospital of Zurich underwent amyloid (A) and tau (T) PET, as well as T1-weigthed MRI scans using site-specific protocols. Subjects were classified by cognition (cognitively unimpaired, CU, or impaired, CI) based on clinical assessment by experts. Amyloid data converted into the standardized centiloid scale, tau PET data normalized to cerebellar uptake, and hippocampal volume expressed as a ratio over total intracranial volume ratio were considered as biomarkers for A, T, and neurodegeneration (N), respectively. Positivity for each biomarker was defined based on previously published thresholds. Subjects were then classified according to the ATN model. Differences among profiles were tested using Kruskal-Wallis ANOVA, and between cohorts using Wilcoxon tests.

RESULTS

Twenty-nine percent of subjects from the Geneva cohorts were classified with a normal (A-T-N-) profile, while the Zurich cohort included 64% of subjects in the same category. Meanwhile, 63% of the Geneva and 16% of the Zurich cohort were classified within the AD continuum (being A+ regardless of other biomarkers' statuses). Within cohorts, ATN profiles were significantly different for age and mini-mental state examination scores, but not for years of education. Age was not significantly different between cohorts. In general, imaging A and T biomarkers were significantly different between cohorts, but they were no longer significantly different when stratifying the cohorts by ATN profile. N was not significantly different between cohorts.

CONCLUSION

Stratifying subjects into ATN profiles provides comparable groups of subjects even when individual recruitment followed different criteria.

In Vitro and In Vivo Evaluation of ABCG2 (BCRP) Inhibitors Derived from Ko143

Breast cancer resistance protein (BCRP, ABCG2) is an efflux transporter that plays a crucial role in multidrug resistance to antineoplastic drugs. Ko143, an analogue of the natural product fumitremorgin C, is a potent inhibitor of ABCG2 but is rapidly hydrolyzed to an inactive metabolite in vivo. To identify ABCG2 inhibitors with improved metabolic stability, we have assessed a series of Ko143 analogues for their ability to inhibit ABCG2-mediated transport in ABCG2-transduced MDCK II cells and determined the stability of the most potent compounds in liver microsomes. The most promising analogues were evaluated in vivo by positron emission tomography. In vitro, three of the tested analogues were potent ABCG2 inhibitors and stable in microsomes. In vivo, they increased the distribution of the ABCG2/ABCB1 substrate [¹¹C]tariquidar to the brain both in wild-type (with Abcb1a/b transport blocked by tariquidar) and Abcb1a/b(-/-) mice. One analogue was more potent than Ko143 in both animal models.

[Clinical analysis of liver dysfunction induced by SHR-1210 alone or combined with apatinib and chemotherapy in patients with advanced esophageal squamous cell carcinoma]

Objective: To investigate the clinical characteristics of abnormal liver function in patients with advanced esophageal squamous carcinoma treated with programmed death-1 (PD-1) antibody SHR-1210 alone or in combination with apatinib and chemotherapy. Methods: Clinical data of 73 patients with esophageal squamous carcinoma from 2 prospective clinical studies conducted at the Cancer Hospital Chinese Academy of Medical Sciences from May 11, 2016, to November 19, 2019, were analyzed, and logistic regression analysis was used for the analysis of influencing factors. Results: Of the 73 patients, 35 had abnormal liver function. 13 of the 43 patients treated with PD-1 antibody monotherapy (PD-1 monotherapy group) had abnormal liver function, and the median time to first abnormal liver function was 55 days. Of the 30 patients treated with PD-1 antibody in combination with apatinib and chemotherapy (PD-1 combination group), 22 had abnormal liver function, and the median time to first abnormal liver function was 41 days. Of the 35 patients with abnormal liver function, 2 had clinical symptoms, including malaise and loss of appetite, and 1 had jaundice. 28 of the 35 patients with abnormal liver function returned to normal and 7 improved to grade 1, and none of the patients had serious life-threatening or fatal liver function abnormalities. Combination therapy was a risk factor for patients to develop abnormal liver function (P=0.007). Conclusions: Most of the liver function abnormalities that occur during treatment with PD-1 antibody SHR-1210 alone or in combination with apatinib and chemotherapy are mild, and liver function can return to normal or improve with symptomatic treatment. For patients who receive PD-1 antibody in combination with targeted therapy and chemotherapy and have a history of long-term previous smoking, alcohol consumption and hepatitis B virus infection, liver function should be monitored and actively managed in a timely manner.

Capillary-driven horseshoe vortex forming around a micro-pillar

HYPOTHESIS

Horseshoe vortices are known to emerge around large-scale obstacles, such as bridge pillars, due to an inertia-driven adverse pressure gradient forming on the upstream-side of the obstacle. We contend that a similar flow structure can arise in thin-film Stokes flow around micro-obstacles, such as used in textured surfaces to improve wettability. This could be exploited to enhance mixing in microfluidic devices, typically limited to creeping-flow regimes.

EXPERIMENTS

Numerical simulations based on the Navier-Stokes equations are carried out to elucidate the flow structure associated with the wetting dynamics of a liquid film spreading around a 50 μm diameter micro-pillar. The employed multiphase solver, which is based on the volume of fluid method, accurately reproduces the wetting dynamics observed in current and previous (Mu et al., Langmuir, 2019) experiments.

FINDINGS

The flow structure within the liquid meniscus forming at the foot of the micro-pillar evinces a horseshoe vortex wrapping around the obstacle, notwithstanding that the Reynolds number in our system is extremely low. Here, the adverse pressure gradient driving flow reversal near the bounding wall is caused by capillarity instead of inertia. The horseshoe vortex is entangled with other vortical structures, leading to an intricate flow system with high-potential mixing capabilities.

Rest/stress myocardial perfusion imaging by positron emission tomography with 18F-Flurpiridaz: A feasibility study in mice

BACKGROUND

Myocardial perfusion imaging by positron emission tomography (PET-MPI) is the current gold standard for quantification of myocardial blood flow. 18F-flurpiridaz was recently introduced as a valid alternative to currently used PET-MPI probes. Nonetheless, optimum scan duration and time interval for image analysis are currently unknown. Further, it is unclear whether rest/stress PET-MPI with 18F-flurpiridaz is feasible in mice.

METHODS

Rest/stress PET-MPI was performed with 18F-flurpiridaz (0.6-3.0 MBq) in 27 mice aged 7-8 months. Regadenoson (0.1 µg/g) was used for induction of vasodilator stress. Kinetic modeling was performed using a metabolite-corrected arterial input function. Image-derived myocardial 18F-flurpiridaz uptake was assessed for different time intervals by placing a volume of interest in the left ventricular myocardium.

RESULTS

Tracer kinetics were best described by a two-tissue compartment model. K1 ranged from 6.7 to 20.0 mL·cm-3·min-1, while myocardial volumes of distribution (VT) were between 34.6 and 83.6 mL·cm-3. Of note, myocardial 18F-flurpiridaz uptake (%ID/g) was significantly correlated with K1 at rest and following pharmacological vasodilation for all time intervals assessed. However, while Spearman's coefficients (rs) ranged between 0.478 and 0.681, R2 values were generally low. In contrast, an excellent correlation of myocardial 18F-flurpiridaz uptake with VT was obtained, particularly when employing the averaged myocardial uptake from 20 to 40 min post tracer injection (R2 ≥ 0.98). Notably, K1 and VT were similarly sensitive to pharmacological vasodilation induction. Further, mean stress-to-rest ratios of K1, VT, and %ID/g 18F-flurpiridaz were virtually identical, suggesting that %ID/g 18F-flurpiridaz can be used to estimate coronary flow reserve (CFR) in mice.

CONCLUSION

Our findings suggest that a simplified assessment of relative myocardial perfusion and CFR, based on image-derived tracer uptake, is feasible with 18F-flurpiridaz in mice, enabling high-throughput mechanistic CFR studies in rodents.

In vivo Imaging of Cannabinoid Type 2 Receptors: Functional and Structural Alterations in Mouse Model of Cerebral Ischemia by PET and MRI

PURPOSE

Stroke is one of the most prevalent vascular diseases. Non-invasive molecular imaging methods have the potential to provide critical insights into the temporal dynamics and follow alterations of receptor expression and metabolism in ischemic stroke. The aim of this study was to assess the cannabinoid type 2 receptor (CB2R) levels in transient middle cerebral artery occlusion (tMCAO) mouse models at subacute stage using positron emission tomography (PET) with our novel tracer [18F]RoSMA-18-d6 and structural imaging by magnetic resonance imaging (MRI).

PROCEDURES

Our recently developed CB2R PET tracer [18F]RoSMA-18-d6 was used for imaging neuroinflammation at 24 h after reperfusion in tMCAO mice. The RNA expression levels of CB2R and other inflammatory markers were analyzed by quantitative real-time polymerase chain reaction using brain tissues from tMCAO (1 h occlusion) and sham-operated mice. [18F]fluorodeoxyglucose (FDG) was included for evaluation of the cerebral metabolic rate of glucose (CMRglc). In addition, diffusion-weighted imaging and T2-weighted imaging were performed for anatomical reference and delineating the lesion in tMCAO mice.

RESULTS

mRNA expressions of inflammatory markers TNF-α, Iba1, MMP9 and GFAP, CNR2 were increased to 1.3-2.5 fold at 24 h after reperfusion in the ipsilateral compared to contralateral hemisphere of tMCAO mice, while mRNA expression of the neuronal marker MAP-2 was markedly reduced to ca. 50 %. Reduced [18F]FDG uptake was observed in the ischemic striatum of tMCAO mouse brain at 24 h after reperfusion. Although higher activity of [18F]RoSMA-18-d6 in ex vivo biodistribution studies and higher standard uptake value ratio (SUVR) were detected in the ischemic ipsilateral compared to contralateral striatum in tMCAO mice, the in vivo specificity of [18F]RoSMA-18-d6 was confirmed only in the CB2R-rich spleen.

CONCLUSIONS

This study revealed an increased [18F]RoSMA-18-d6 measure of CB2R and a reduced [18F]FDG measure of CMRglc in the ischemic striatum of tMCAO mice at subacute stage. [18F]RoSMA-18-d6 might be a promising PET tracer for detecting CB2R alterations in animal models of neuroinflammation without neuronal loss.

Evaluation of cannabinoid type 2 receptor expression and pyridine-based radiotracers in brains from a mouse model of Alzheimer’s disease

Neuroinflammation plays an important role in the pathophysiology of Alzheimer’s disease. The cannabinoid type 2 receptor (CB2R) is an emerging target for neuroinflammation and therapeutics of Alzheimer’s disease. Here, we aim to assess the alterations in brain CB2R levels and evaluate novel CB2R imaging tracers in the arcAß mouse model of Alzheimer’s disease amyloidosis. Immunohistochemical staining for amyloid-ß deposits (6E10), microgliosis (anti-Iba1 and anti-CD68 antibodies), astrocytes (GFAP) and the anti-CB2R antibody was performed on brain slices from 17-month-old arcAß mice. Autoradiography using the CB2R imaging probes [18F]RoSMA-18-d6, [11C]RSR-056, and [11C]RS-028 and mRNA analysis were performed in brain tissue from arcAß and non-transgenic littermate (NTL) mice at 6, 17, and 24 months of age. Specific increased CB2R immunofluorescence intensities on the increased number of GFAP-positive astrocytes and Iba1-positive microglia were detected in the hippocampus and cortex of 17-month-old arcAß mice compared to NTL mice. CB2R immunofluorescence was higher in glial cells inside 6E10-positive amyloid-ß deposits than peri-plaque glial cells, which showed low background immunofluorescence in the hippocampus and cortex of 17-month-old arcAß mice. Ex vivo autoradiography showed that the specific binding of [18F]RoSMA-18-d6 and [11C]RSR-056 was comparable in arcAß and NTL mice at 6, 17, and 24 months of age. The level of Cnr2 mRNA expression in the brain was not significantly different between arcAß and NTL mice at 6, 17, or 24 months of age. In conclusion, we demonstrated pronounced specific increases in microglial and astroglial CB2R expression levels in a mouse model of AD-related cerebral amyloidosis, emphasizing CB2R as a suitable target for imaging neuroinflammation.

Multi-parameter optimization: Development of a morpholin-3-one derivative with an improved kinetic profile for imaging monoacylglycerol lipase in the brain

Monoacylglycerol lipase (MAGL) is a gatekeeper in regulating endocannabinoid signaling and has gained substantial attention as a therapeutic target for neurological disorders. We recently discovered a morpholin-3-one derivative as a novel scaffold for imaging MAGL via positron emission tomography (PET). However, its slow kinetics in vivo hampered the application. In this study, structural optimization was conducted and eleven novel MAGL inhibitors were designed and synthesized. Based on the results from MAGL inhibitory potency, in vitro metabolic stability and surface plasmon resonance assays, we identified compound 7 as a potential MAGL PET tracer candidate. [¹¹C]7 was synthesized via direct ¹¹CO₂ fixation method and successfully mapped MAGL distribution patterns on rodent brains in in vitro autoradiography. PET studies in mice using [¹¹C]7 demonstrated its improved kinetic profile compared to the lead structure. Its high specificity in vivo was proved by using MAGL KO mice. Although further studies confirmed that [¹¹C]7 is a P-glycoprotein (P-gp) substrate in mice, its low P-gp efflux ratio on cells transfected with human protein suggests that it should not be an issue for the clinical translation of [¹¹C]7 as a novel reversible MAGL PET tracer in human subjects. Overall, [¹¹C]7 ([¹¹C]RO7284390) showed promising results warranting further clinical evaluation.

P-355 Association between high serum uric acid level and adverse reproductive outcomes in infertile women with polycystic ovary syndrome

Study question

Does high serum uric acid (SUA) level affect the reproductive outcomes in women with polycystic ovary syndrome (PCOS) undergoing in-vitro fertilization (IVF)?

Summary answer

Elevated SUA is associated with decreased live birth rate, biochemical pregnancy rate and clinical pregnancy rate, and increased miscarriage rate in women with PCOS.

What is known already

SUA levelsand the prevalence of hyperuricemia (25.48%) are both significantly higher in women with PCOS than in women without PCOS (8.74%). SUA levels also can be used as a predictor of pregnancy complications (gestational diabetes mellitus and hypertensive disorders of pregnancy) and adverse foetal outcomes (preterm birth and low birth weight).

Study design, size, duration

This retrospective cohort study was conducted ininfertile women with PCOS between September 2012 and December 2019.

Participants/materials, setting, methods

A total of 1,032 infertile PCOS women undergoing their first IVF/ICSI cycle were observed. Data of reproductive outcomes including live birth rate, biochemical pregnancy rate, clinical pregnancy rate, and miscarriage rate were analyzed according to the quartile groups of SUA levels.

Main results and the role of chance

In quartiles of SUA levels, there was a significant decreasing trend in live birth rate from the lowest quartile (Q1: 34.5%) to the highest (Q4: 19.2%) (Pfor trend &lt;0.001). Notably, the miscarriage rate in Q4 was significantly higher than that in the other 3 quartiles (all P values &lt; 0.05). From Q1 to Q4, the incidence of miscarriage dramatically increased from 15.5% to 31.0% (Pfor trend &lt;0.05). In addition, the biochemical pregnancy rate and clinical pregnancy rate decreased significantly from the lowest quartile to the highest (Pfor trend &lt;0.05). With the first quartile of uric acid as the reference group, the logistic regression analysis showed that in both unadjusted and adjusted models, elevated SUA level was associated with significantly lower probabilities of live birth, biochemical pregnancy, and clinical pregnancy, and a higher risk of miscarriage in a linear fashion (all Pfor trend&lt; 0.05).

Limitations, reasons for caution

This study is limited by its retrospective design. It was difficult to ensure consistency in clinical practice among the physicians.

Wider implications of the findings

Our study suggeststhat clinical physicians need to pay close attention to PCOS women with high SUA levelsbefore IVF treatment. Prospective studies to determine an appropriate range of lower-SUA levels prior to treatment is necessary to support our findings.

Trial registration number

not applicable

Development of High Brain-Penetrant and Reversible Monoacylglycerol Lipase PET Tracers for Neuroimaging

Monoacylglycerol lipase (MAGL) is one of the key enzymes in the endocannabinoid system. Inhibition of MAGL has been proposed as an attractive approach for the treatment of various diseases. In this study, we designed and successfully synthesized two series of piperazinyl pyrrolidin-2-one derivatives as novel reversible MAGL inhibitors. (R)-[¹⁸F]13 was identified through the preliminary evaluation of two carbon-11-labeled racemic structures [¹¹C]11 and [¹¹C]16. In dynamic positron-emission tomography (PET) scans, (R)-[¹⁸F]13 showed a heterogeneous distribution and matched the MAGL expression pattern in the mouse brain. High brain uptake and brain-to-blood ratio were achieved by (R)-[¹⁸F]13 in comparison with previously reported reversible MAGL PET radiotracers. Target occupancy studies with a therapeutic MAGL inhibitor revealed a dose-dependent reduction of (R)-[¹⁸F]13 accumulation in the mouse brain. These findings indicate that (R)-[¹⁸F]13 ([¹⁸F]YH149) is a highly promising PET probe for visualizing MAGL non-invasively in vivo and holds great potential to support drug development.

Role of sex hormones in modulating myocardial perfusion and coronary flow reserve

Background

A growing body of evidence highlights sex differences in the diagnostic accuracy of cardiovascular imaging modalities. Nonetheless, the role of sex hormones in modulating myocardial perfusion and coronary flow reserve (CFR) is currently unclear. The aim of our study was to assess the impact of female and male sex hormones on myocardial perfusion and CFR.

Methods

Rest and stress myocardial perfusion imaging (MPI) was conducted by small animal positron emission tomography (PET) with [¹⁸F]flurpiridaz in a total of 56 mice (7–8 months old) including gonadectomized (Gx) and sham-operated males and females, respectively. Myocardial [¹⁸F]flurpiridaz uptake (% injected dose per mL, % ID/mL) was used as a surrogate for myocardial perfusion at rest and following intravenous regadenoson injection, as previously reported. Apparent coronary flow reserve (CFR_App) was calculated as the ratio of stress and rest myocardial perfusion. Left ventricular (LV) morphology and function were assessed by cardiac magnetic resonance (CMR) imaging.

Results

Orchiectomy resulted in a significant decrease of resting myocardial perfusion (Gx vs. sham, 19.4 ± 1.0 vs. 22.2 ± 0.7 % ID/mL, p = 0.034), while myocardial perfusion at stress remained unchanged (Gx vs. sham, 27.5 ± 1.2 vs. 27.3 ± 1.2 % ID/mL, p = 0.896). Accordingly, CFR_App was substantially higher in orchiectomized males (Gx vs. sham, 1.43 ± 0.04 vs. 1.23 ± 0.05, p = 0.004), and low serum testosterone levels were linked to a blunted resting myocardial perfusion (r = 0.438, p = 0.020) as well as an enhanced CFR_App (r = −0.500, p = 0.007). In contrast, oophorectomy did not affect myocardial perfusion in females. Of note, orchiectomized males showed a reduced LV mass, stroke volume, and left ventricular ejection fraction (LVEF) on CMR, while no such effects were observed in oophorectomized females.

Conclusion

Our experimental data in mice indicate that sex differences in myocardial perfusion are primarily driven by testosterone. Given the diagnostic importance of PET-MPI in clinical routine, further studies are warranted to determine whether testosterone levels affect the interpretation of myocardial perfusion findings in patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-022-05675-2.

Lactobacillus plantarum and molasses alter dynamic chemical composition, microbial community, and aerobic stability of mixed (amaranth and rice straw) silage

BACKGROUND

The objective was to determine how molasses and Lactobacillus plantarum affect chemical composition, fermentation quality, aerobic stability, and the microbial community of an ensiled mixture of amaranth (Amaranthus hypochondriaus, AF) and rice straw. Treatments were control (C, no addition), L. plantarum (L; 2 × 10⁵  cfu g^-1 fresh weight), molasses (M; 40 g kg^-1 fresh matter), and their combination (LM). All treatments were ensiled for 1, 3, 5, 7, and 30 days.

RESULTS

All additives improved fermentation quality with greater lactic acid (LA), acetic acid, and lower pH than C silage over the ensiling period. The LM silage combination optimized fermentability, manifested as greater LA contents and a more rapid pH reduction during the first 7 days of ensiling than L or M silages. After 30 days of ensiling, inoculant L. plantarum increased Lactobacillus abundance and reduced bacterial diversity and Enterobacteriaceae abundance compared with silage treated with molasses. Molasses addition reduced the relative concentration of structural carbohydrates (neutral and acid detergent fiber, and hemicellulose) after 30 days of ensiling. Finally, there was spoilage after 2 days and 4 days of aerobic exposure in C and LM silages respectively, whereas L silage had not spoiled after 4 days.

CONCLUSIONS

Although the combination of L. plantarum and molasses further optimized fermentation characteristics, L silage had better aerobic stability. © 2021 Society of Chemical Industry.

Measurements of neutral particle energy spectrum on EAST using a time-of-flight low-energy neutral particle analyzer

The neutral particles generated by charge exchange reactions can play an important role in erosion of first wall materials in fusion devices. In order to measure the flux and energy of neutral particles to the first wall, a low-energy neutral particle analyzer (LENPA) based on the time-of-flight method has been developed and successfully applied on the Experimental Advanced Superconducting Tokamak (EAST)' to measure the neutrals with an energy of 20-3000 eV. The LENPA works in the counting mode, and the signal of photons is used as the reference for the flight time of neutrals. The energy spectrum of low-energy neutral particles on EAST has been obtained for the first time. The new diagnostics can help in understanding the neutral particle generation and deposition on the first wall materials in tokamaks under different plasma conditions.

Tauvid™: The First FDA-Approved PET Tracer for Imaging Tau Pathology in Alzheimer's Disease

Tauvid has been approved by the U.S. Food and Drug Administration (FDA) in 2020 for positron emission tomography (PET) imaging of adult patients with cognitive impairments undergoing evaluation for Alzheimer’s disease (AD) based on tau pathology. Abnormal aggregation of tau proteins is one of the main pathologies present in AD and is receiving increasing attention as a diagnostic and therapeutic target. In this review, we summarised the production and quality control of Tauvid, its clinical application, pharmacology and pharmacokinetics, as well as its limitation due to off-target binding. Moreover, a brief overview on the second-generation of Tau PET tracers is provided. The approval of Tauvid marks a step forward in the field of AD research and opens up opportunities for second-generation tau tracers to advance tau PET imaging in the clinic.

Eicosapentaenoic acid enhances skeletal muscle hypertrophy without altering the protein anabolic signaling pathway

This study aimed to examine the effect of eicosapentaenoic acid (EPA) on skeletal muscle hypertrophy induced by muscle overload and the associated intracellular signaling pathways. Male C57BL/6J mice were randomly assigned to oral treatment with either EPA or corn oil for 6 weeks. After 4 weeks of treatment, the gastrocnemius muscle of the right hindlimb was surgically removed to overload the plantaris and soleus muscles for 1 or 2 weeks. We examined the effect of EPA on the signaling pathway associated with protein synthesis using the soleus muscles. According to our analysis of the compensatory muscle growth, EPA administration enhanced hypertrophy of the soleus muscle but not hypertrophy of the plantaris muscle. Nevertheless, EPA administration did not enhance the expression or phosphorylation of Akt, mechanistic target of rapamycin (mTOR), or S6 kinase (S6K) in the soleus muscle. In conclusion, EPA enhances skeletal muscle hypertrophy, which can be independent of changes in the AKT-mTOR-S6K pathway.

Positron Emission Tomography Imaging of the Endocannabinoid System: Opportunities and Challenges in Radiotracer Development

The endocannabinoid system (ECS) is involved in a wide range of biological functions and comprises cannabinoid receptors and enzymes responsible for endocannabinoid synthesis and degradation. Over the past 2 decades, significant advances toward developing drugs and positron emission tomography (PET) tracers targeting different components of the ECS have been made. Herein, we summarized the recent development of PET tracers for imaging cannabinoid receptors 1 (CB1R) and 2 (CB2R) as well as the key enzymes monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), particularly focusing on PET neuroimaging applications. State-of-the-art PET tracers for the ECS will be reviewed including their chemical design, pharmacological properties, radiolabeling, as well as preclinical and human PET imaging. In addition, this review addresses the current challenges for ECS PET biomarker development and highlights the important role of PET ligands to study disease pathophysiology as well as to facilitate drug discovery.

Neuroimaging with Radiopharmaceuticals Targeting the Glutamatergic System

Radiopharmacy at ETH has worked on the development of novel PET tracers for neuro-, cardiac- and tumor imaging for many years. In this paper, our efforts on targeting the glutamatergic system of the metabotropic glutamate receptor subtype 5 (mGluR5) and the ionotropic N-methyl-<small>D</small>-aspartate (NMDA) receptor are summarized. We briefly described the principles of positron emission tomography (PET) tracer development for the central nervous system (CNS) and the radiolabeling methods used in our laboratory. To assess the radioligands, results of in vitro autoradiography, biodistribution, and metabolite studies as well as PET imaging data are discussed. Furthermore, key PET parameters for kinetic modeling and quantification methods are provided. Two mGluR5 PET tracers, [11C]ABP688 and [18F]PSS232, were translated in our GMP labs and evaluated in human subjects. The newly developed GluN2B PET tracer [11C]Me-NB1 is currently being investigated in a first-in-human PET study and several F-18 labeled tracers are being evaluated in non-human primates in which the first-in-class will be translated for human studies.

Evaluation of 5H-Thiazolo[3,2-α]pyrimidin-5-ones as Potential GluN2A PET Tracers

We describe here our efforts to develop a PET tracer for imaging GluN2A-containing NMDA receptors, based on a 5H-thiazolo[3,2-α]pyrimidin-5-one scaffold. The metabolic stability and overall properties could be optimized satisfactorily, although binding affinities remained a limiting factor for in vivo imaging. We nevertheless identified 7-(((2-fluoroethyl)(3-fluorophenyl)amino)-methyl)-3-(2-(hydroxymethyl)cyclopropyl)-2-methyl-5H-thiazolo-[3,2-α]pyrimidin-5-one ([¹⁸ F]7b) as a radioligand providing good-quality images in autoradiographic studies, as well as a tritiated derivative, 2-(7-(((2-fluoroethyl)(4-fluorophenyl)amino)methyl)-2-methyl-5-oxo-5H-thiazolo[3,2-α]pyrimidin-3-yl)cyclopropane-1-carbonitrile ([³ H₂ ]15b), which was used for the successful development of a radioligand binding assay. These are valuable new tools for the study of GluN2A-containing NMDA receptors, and for the optimization of allosteric modulators binding to the pharmacophore located at the dimer interface of the GluN1-GluN2A ligand-binding domain.

On the consensus nomenclature rules for radiopharmaceutical chemistry - Reconsideration of radiochemical conversion

Radiochemical conversion is an important term to be included in the "Consensus nomenclature rules for radiopharmaceutical chemistry". Radiochemical conversion should be used to define reaction efficiency by measuring the transformation of components in a crude reaction mixture at a given time, whereas radiochemical yield is better suited to define the efficiency of an entire reaction process including, for example, separation, isolation, filtration, and formulation.

Obesity prevalence and risks among Chinese adults: findings from China PEACE Million Persons Project, 2014–2018

Background

With demographic and epidemiologic transitions, China has become home to the greatest number of obese individuals in the world. Effective policy intervention requires a contemporary assessment of obesity across broad socio-demographic subgroups.

Purpose

We aim to assess the prevalence of overall and abdominal obesity by socio-demographic characteristics and the associations of these characteristics with obesity in China.

Methods

Using the data of 2.7-million community-dwelling participants aged 35–75 years in the China PEACE Million Persons Project, a nationwide cross-sectional screening project from 2014 to 2018, we calculated the prevalence of overall and abdominal obesity based on national guideline definitions (body mass index ≥28 kg/m2, waist circumference ≥85/90 cm for women/men). We examined 12 available socio-demographic variables that are potentially associated with obesity, in addition to self-reported co-morbidities, and quantified the associations of these socio-demographic characteristics with obesity using multivariable mixed models.

Results

The prevalence of overall and abdominal obesity were 15.8% and 37.6% in women and 15.0% and 36.3% in men (Figure). Compared to individuals with normal weight, those with overall obesity had a higher prevalence of hypertension, dyslipidemia, and diabetes (in women: by 30.4, 16.1, and 6.0 percent points; in men, by 29.9, 31.2, and 5.8 percent points). A similar pattern was observed with abdominal obesity. In women, those aged 55–64 years constituted the largest age group with overall and abdominal obesity (33.7% and 35.0%), while in men, those aged 45–54 and 55–64 years constituted the largest age group with overall obesity (30.4%) and abdominal obesity (30.5%), respectively. Older women were at substantially higher risk for obesity (e.g., adjusted relative risk [95% CI] of women aged 65–75 vs. 35–44 years: 1.29 [1.27–1.31] for overall obesity and 1.76 [1.74–1.77] for abdominal obesity) while older men were not. Higher education was associated with lower risk in women (e.g., those with college or university education vs. less than primary school: 0.47 [0.46–0.48] for overall obesity and 0.61 [0.60–0.62] for abdominal obesity) but higher risk in men (1.07 [1.05–1.10] and 1.17 [1.16–1.19]). In both women and men, current smoking was associated with lower risk for obesity, and current drinking was associated with higher risk, but the magnitude of associations was smaller in women than men.

Conclusions

In China, over one in seven individuals meet criteria for overall obesity, and one in three for abdominal obesity. Wide variation exists across socio-demographic subgroups. The associations of age and education with obesity are significant and differ by sex. Understanding obesity in contemporary China has broad domestic policy implications and provides a valuable international reference.

Figure 1

Funding Acknowledgement

Type of funding source: Other. Main funding source(s): The National Key Research and Development Program from the Ministry of Science and Technology of China, the CAMS Innovation Fund for Medical Science

Age-dependent cardiac remodelling – role of sex hormones

Background

While cardiovascular mortality in women has exceeded those in men, women continue to be underrepresented in cardiovascular clinical trials. Further, preclinical experiments are predominantly conducted in male animals, rendering sex-specific variables contributing to cardiovascular disease largely unknown. As age and menopause remain to be key risk factors for cardiovascular disease in women, the aim of this study was to identify key variables of cardiac remodelling in the aging female and male heart, as well as to assess effects of sex hormone deprivation on left ventricular (LV) morphology, LV function and cardiac sympathetic activity.

Materials and methods

Gonadectomized and sham-operated FVB/N mice of both sexes were subjected to positron emission tomography (PET) and cardiac magnetic resonance (CMR) imaging at the age of 4 (young cohort) and 20 (aged cohort) months (total n=123, 55% females). Following tail-vein injection of [11C]meta-hydroxynorephedrine ([11C]mHED), a widely used PET probe in preclinical and clinical assessment of cardiac sympathetic integrity, animals were scanned and cardiac sympathetic outflow was derived from myocardial [11C]mHED uptake. Cardiac parameters including LV volumes and left ventricular ejection fraction (LVEF) were obtained from electrocardiogram (ECG)-gated CMR imaging.

Results and discussion

A significant increase of LVEF was observed in aging females (p=0.012, Figure 1), but not in males. The latter was not associated with a higher cardiac output, and was a consequence of reduced LV end-systolic volumes (p=0.008), unveiling a substantial reduction of size in the aging female heart. As this age-dependent observation was not present in gonadectomized animals (p=0.414), the lack of growth-stimulating estrogen might account for reduction of cardiac size in aging females. Thus, despite a significantly heightened body weight, female heart size is reduced with age. Accordingly, sufficient cardiac output was maintained via increased heart rate (p=0.005) and cardiac sympathetic activity (p=0.040, Figure 1). Gonadectomy accelerated age-dependent changes in LV morphology and function in female mice. While sex hormone deprivation blunted cardiac sympathetic activity and norepinephrine levels in male mice, an opposite trend was observed in females.

Conclusion

Despite increasing body weight with age, aged female and male hearts maintain a stable circulatory blood supply, however, by distinct mechanisms. While the “shrinking” female heart requires an increased heart rate and cardiac sympathetic activity to compensate for smaller ventricular volumes, aging males maintain cardiac size. Importantly, sex hormone deprivation at a young age accelerates age-dependent changes in LV morphology and function in female mice, but not in male mice. The increased sympathetic activity reflects a higher stress level in aged females that might expose them to a higher cardiac vulnerability at postmenopausal age.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Swiss National Science Foundation; Swissheart Foundation

[11C]mHED PET follows a two-tissue compartment model in mouse myocardium with norepinephrine transporter (NET)-dependent uptake, while [18F]LMI1195 uptake is NET-independent

PURPOSE

Clinical positron emission tomography (PET) imaging of the presynaptic norepinephrine transporter (NET) function provides valuable diagnostic information on sympathetic outflow and neuronal status. As data on the NET-targeting PET tracers [¹¹C]meta-hydroxyephedrine ([¹¹C]mHED) and [¹⁸F]LMI1195 ([¹⁸F]flubrobenguane) in murine experimental models are scarce or lacking, we performed a detailed characterization of their myocardial uptake pattern and investigated [¹¹C]mHED uptake by kinetic modelling.

METHODS

[¹¹C]mHED and [¹⁸F]LMI1195 accumulation in the heart was studied by PET/CT in FVB/N mice. To test for specific uptake by NET, desipramine, a selective NET inhibitor, was administered by intraperitoneal injection. [¹¹C]mHED kinetic modelling with input function from an arteriovenous shunt was performed in three mice.

RESULTS

Both tracers accumulated in the mouse myocardium; however, only [¹¹C]mHED uptake was significantly reduced by excess amount of desipramine. Myocardial [¹¹C]mHED uptake was half-saturated at 88.3 nmol/kg of combined mHED and metaraminol residual. After [¹¹C]mHED injection, a radiometabolite was detected in plasma and urine, but not in the myocardium. [¹¹C]mHED kinetics followed serial two-tissue compartment models with desipramine-sensitive K₁.

CONCLUSION

PET with [¹¹C]mHED but not [¹⁸F]LMI1195 provides information on NET function in the mouse heart. [¹¹C]mHED PET is dose-independent in the mouse myocardium at < 10 nmol/kg of combined mHED and metaraminol. [¹¹C]mHED kinetics followed serial two-tissue compartment models with K₁ representing NET transport. Myocardial [¹¹C]mHED uptake obtained from PET images may be used to assess cardiac sympathetic integrity in mouse models of cardiovascular disease.

Identification and Preclinical Development of a 2,5,6-Trisubstituted Fluorinated Pyridine Derivative as a Radioligand for the Positron Emission Tomography Imaging of Cannabinoid Type 2 Receptors

Despite the broad implications of the cannabinoid type 2 receptor (CB2) in neuroinflammatory processes, a suitable CB2-targeted probe is currently lacking in clinical routine. In this work, we synthesized 15 fluorinated pyridine derivatives and tested their binding affinities toward CB2 and CB1. With a sub-nanomolar affinity (K_i for CB2) of 0.8 nM and a remarkable selectivity factor of >12,000 over CB1, RoSMA-18-d₆ exhibited outstanding in vitro performance characteristics and was radiofluorinated with an average radiochemical yield of 10.6 ± 3.8% (n = 16) and molar activities ranging from 52 to 65 GBq/μmol (radiochemical purity > 99%). [¹⁸F]RoSMA-18-d₆ showed exceptional CB2 attributes as demonstrated by in vitro autoradiography, ex vivo biodistribution, and positron emission tomography (PET). Further, [¹⁸F]RoSMA-18-d₆ was used to detect CB2 upregulation on postmortem human ALS spinal cord tissues. Overall, these results suggest that [¹⁸F]RoSMA-18-d₆ is a promising CB2 PET radioligand for clinical translation.

Preclinical Development of 18F-OF-NB1 for Imaging GluN2B-Containing N-Methyl-d-Aspartate Receptors and Its Utility as a Biomarker for Amyotrophic Lateral Sclerosis

As part of our continuous efforts to develop a suitable ¹⁸F-labeled PET radioligand with improved characteristics for imaging the N-methyl-d-aspartate receptors (NMDARs) subtype 2B (GluN1/2B), we investigated in the current work ortho-fluorinated (OF) and meta-fluorinated (MF) analogs of ¹⁸F-para-fluorinated (PF)-NB1, a 3-benzazepine-based radiofluorinated probe. Methods: OF-NB1 and MF-NB1 were prepared using a multistep synthesis, and their binding affinities toward GluN2B subunits and selectivity over σ1 receptors (σ1Rs) were determined via competitive binding assays. ¹⁸F-OF-NB1 was synthesized via copper-mediated radiofluorination and was evaluated in Wistar rats by in vitro autoradiography, PET imaging, ex vivo biodistribution, metabolite experiments, and receptor occupancy studies using CP-101,606, an established GluN2B antagonist. To determine in vivo selectivity, ¹⁸F-OF-NB1 was validated in wild-type and σ1R knock-out mice. Translational relevance was assessed in autoradiographic studies using postmortem human brain tissues from healthy individuals and ALS patients, the results of which were corroborated by immunohistochemistry. Results: The binding affinity values for OF-NB1 and MF-NB1 toward the GluN2B subunits were 10.4 ± 4.7 and 590 ± 36 nM, respectively. For σ1R binding, OF-NB1 and MF-NB1 exhibited inhibition constants of 410 and 2,700 nM, respectively. OF-NB1, which outperformed MF-NB1, was radiolabeled with ¹⁸F to afford ¹⁸F-OF-NB1 in more than 95% radiochemical purity and molar activities of 192 ± 33 GBq/μmol. In autoradiography experiments, ¹⁸F-OF-NB1 displayed a heterogeneous and specific binding in GluN2B subunit-rich brain regions such as the cortex, striatum, hypothalamus, and hippocampus. PET imaging studies in Wistar rats showed a similar heterogeneous uptake, and no brain radiometabolites were detected. A dose-dependent blocking effect was observed with CP-101,606 (0.5-15 mg/kg) and resulted in a 50% receptor occupancy of 8.1 μmol/kg. Postmortem autoradiography results revealed lower expression of the GluN2B subunits in ALS brain tissue sections than in healthy controls, in line with immunohistochemistry results. Conclusion: ¹⁸F-OF-NB1 is a highly promising PET probe for imaging the GluN2B subunits of the N-methyl-d-aspartate receptor. It possesses utility for receptor occupancy studies and has potential for PET imaging studies in ALS patients and possibly other brain disorders.

Development of a quartz crystal microbalance diagnostic for measuring material erosion and deposition on the first wall in EAST

A quartz crystal microbalance (QMB) diagnostic system has been established in Experimental Advanced Superconducting Tokamak (EAST) for real-time and in situ measurements of erosion and deposition rates of plasma-facing materials at the first wall. A ∼70 nm aluminum (Al) film has been coated on the QMB crystal surface to measure the erosion rate by charge exchange neutral particles. Dual sensors of the QMB system have been used with a closed sensor for reference. The stability and light sensitivity of the QMB system have been tested in the lab, demonstrating its feasibility on the application of EAST experiments. The QMB system with cooling water has been successfully applied in the 2018 EAST campaign. The net erosion thickness measured by the QMB has been well validated by thickness measurements using the Rutherford backscattering spectrometry. The developed QMB systems can help us to understand the physics processes of material erosion and deposition at main chamber walls for long pulse operations in EAST.

OP0093 FREQUENCIES AND PREDICTORS OF THE LUPUS LOW DISEASE ACTIVITY STATE AND REMISSION IN TREATMENT-NAÏVE PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS -- A REAL-WORLD COHORT STUDY

Background:

After the introduction of treat-to-target strategy in systemic lupus erythematosus (SLE), Lupus Low Disease Activity State (LLDAS) and definitions of remission in SLE (DORIS) were developed and validated. Several studies had demonstrated that the achievement and maintenance of LLDAS or DORIS was associated with good prognosis.

Objectives:

To evaluate the attainability of LLDAS and DORIS in a treatment-naïve cohort of SLE.

Methods:

LDAS5 was defined as LLDAS with a prednisone dose ≤5 mg/d. There were 4 definitions in DORIS: clinical remission on treatment (RONT), complete RONT, clinical remission off treatment (ROFT) and complete ROFT. The treatment-naïve patients from Peking University First Hospital SLE cohort were enrolled. The time to each state and their annual cumulative probabilities were estimated by Kaplan-Meier approach. The frequencies of patients who achieved each component of LLDAS or DORIS during follow-up were determined.

Results:

A total of 218 treatment-naïve patients were included, with a median follow-up of 4.48 years. Respectively, 190 (87.2%), 160 (73.4%), 148 (67.9%), 94 (43.1%), 23 (10.6%) and 18 (8.3%) patients achieved LLDAS, LLDAS5, clinical RONT, complete RONT, clinical ROFT and complete ROFT at least once during the follow-up time. The median time to LLDAS, LLDAS5, clinical RONT and complete RONT were 1.4, 2.3, 2.6 and 4.7 years, respectively.

Table 1.

Frequencies, time to achieve and annual cumulative probabilities of each state by Kaplan-Meier approach

StatesAchieved patientsNumber (%)Time to achieve(years)Cumulative probabilities of achievement (%)Year 1Year 2Year 3Year 4Year 5LLDAS190 (87.2)1.418.869.786.789.192.6LLDAS5160 (73.4)2.36.940.763.376.082.3Clinical RONT148 (67.9)2.65.536.156.168.876.6Complete RONT94 (43.1)4.74.122.637.545.350.4Clinical ROFT23 (10.6)NA1.42.95.46.710.6Complete ROFT18 (8.3)NA0.92.54.84.88.8Table 2.

Patients who achieved each component of LLDAS or DORIS during follow-up

ComponentsNumber (%)SLEDAI-2K ≤4, with no activity in major organ systems (renal, central nervous system, cardiopulmonary, vasculitis, fever), and no haemolytic anaemia or gastrointestinal active213 (97.7)Clinical SLEDAI-2K =0210 (96.3)PGA ≤1217 (99.5)PGA <0.5199 (91.3)Serology (anti-dsDNA and complement) negative148 (67.9)Prednisone dose ≤7.5 mg/day201 (92.2)Prednisone dose ≤5 mg/day171 (78.4)No prednisone dose40 (18.3)No prednisone dose and Immunosuppressants32 (14.7)

Conclusion:

Our data confirmed that LLDAS is an attainable early treatment target for SLE. Though with more difficulty, RONT can be achieved in two-thirds of our patients. ROFT may not be an ideal treatment target at present as it is only attained in few patients.

References:

[1]Franklyn, K. et al. Ann Rheum Dis. 2016 Sep;75(9):1615-21.

[2]van Vollenhoven, R. et al. Ann Rheum Dis. 2017 Mar;76(3):554-561.

Disclosure of Interests:

None declared

AB0380 THERAPEUTIC CHOICES AND OUTCOMES IN CHINESE PATIENTS WITH SEROLOGICALLY ACTIVE CLINICALLY QUIESCENT SYSTEMIC LUPUS ERYTHEMATOSUS

Background:

Patients with systemic lupus erythematosus (SLE) who achieved the clinical state as serologically active clinically quiescent (SACQ). It appears to account for 6–12% of all patients with SLE, but there is disagreement about whether such patients are indeed clinically stable [1-3], especially in Chinese patients. And there is no conclusion as to what kind of treatment should be taken for such patients.

Objectives:

To clarify the frequency and outcome of SACQ patients in lupus. And to identify factors associated with the flare of disease.

Methods:

Clinical data of patients diagnosed as SLE and followed in Peking University First Hospital from 2009 to 2015 were retrospectively reviewed. 682 patients with systemic lupus erythematosus who were followed up for more than 6 months at Peking University First Hospital from January 2007 to December 2015 were summarized. SACQ was defined as an at least a 6-month period with persistent serologic activity and without clinical activity and could be taking a daily dose of prednisone or equivalent less than 7.5 mg. Serologically quiescent clinically quiescent (SQCQ) patients and serologically active clinically active (SACA) patients served as control groups. Data including demographics, initial symptoms, duration to SACQ, treatments before and after SACQ, and characteristics of the flare group were analyzed.

Results:

Of the 682 patients, 170 were SACQ patients (24.9%), 187 were SQCQ patients, and 325 were SACA patients (47.7%). SQCQ patients (38.61±15.08 years old) were older at study start than SACQ patients (38.61±15.08 years vs. 32.09±14.35 years, p<0.001), but there was no significant difference between that of SACQ and SACA patients. 56 of the 170 SACQ patients (32.9%) experienced flare. Corticosteroids (OR 1.317, 95% CI 1.131 to 1.534; p<0.001) was an independent risk factor for flare, while antimalarials (OR 0.265, 95% CI 0.118 to 0.599; p=0.001) and immunosuppressants (OR 0.316, 95% CI 0.149 to 0.670; p=0.003) were protective factors.

Conclusion:

About one third of SLE patients with SACQ experience flare, more than that of patients with SQCQ. Thus, approach to prevent relapse in SACQ patient is required. Maintenance therapy of hydroxychloroquine and immunosuppressant agents may be protective and beneficial treatment strategy in these patients need further investigation.

References:

[1]Gladman DD, Urowitz MB, Keystone EC. Serologically active clinically quiescent systemic lupus erythematosus: a discordance between clinical and serologic features. Am J Med 1979; 66:210-5.

[2]Huang WN, Tso TK, Wu HC, Yang HF, Tsay GJ. Impaired phagocytosis of apoptotic cell material in serologically active clinically quiescent patients with systemic lupus erythematosis. Int J Rheum Dis 2016; 19:1310-6.

[3]Steiman AJ, Gladman DD, Ibañez D, Urowitz MB. Prolonged serologically active clinically quiescent systemic lupus erythematosus: frequency and outcome. J Rheumatol 2010; 37:1822-7.

Disclosure of Interests:

None declared

THU0247 FREQUENCY AND PREDICTORS OF THE LUPUS LOW DISEASE ACTIVITY STATE IN CHINESE PATIENTS WITH SYSTEMIC LUPUS ERYTHEMATOSUS: AN OBSERVATIONAL COHORT STUDY

Background:

As a consensus-based definition of minimally acceptable disease activity in systemic lupus erythematosus (SLE), Lupus Low Disease Activity State (LLDAS) has been well-validated and widely accepted. However, no data about the time to LLDAS in Asian ethnicity has been reported so far.

Objectives:

To estimate the time to LLDAS and the predictors of time to LLDAS in our prospective observational cohort of Chinese patients with SLE.

Methods:

Patients were from Peking University First Hospital SLE cohort and those having not fulfilled LLDAS at enrolment were included in this study. The time to LLDAS and annual cumulative probabilities of LLDAS achievement were estimated by the Kaplan-Meier approach. The predictors of time to LLDAS were identified by univariate and multivariable Cox proportional hazards.

Results:

A total of 574 patients with SLE were included and 435 (75.8%) of them achieved LLDAS during a median 4.2 years of follow-up. The median time to LLDAS was 19.0 months and the cumulative probabilities at 1, 2, 3, 5 and 10 years were 19.8%, 57.6%, 72.0%, 85.1% and 98.0%, respectively. In multivariable Cox models, older age at disease onset, treatment-naïve and hydroxychloroquine prescription were found to be independent predictors of shorter time to LLDAS, after adjusted by daily prednisone dose, SLE Disease Activity Index 2000 and physician’s global assessment. Finally, we developed a matrix model based on the identified independent predictors to present the time to LLDAS in patients with respective characteristics.

Conclusion:

Our study proved that LLDAS is attainable as an early treatment target for SLE in Chinese patients. The older age at disease onset, treatment-naïve and hydroxychloroquine prescription were independent predictors of shorter time to LLDAS.

References:

[1]Franklyn K, Lau CS, Navarra SV, Louthrenoo W, Lateef A, Hamijoyo L, Wahono CS, Chen SL, Jin O, Morton S, Hoi A, Huq M, Nikpour M, Morand EF; Asia-Pacific Lupus Collaboration. Ann Rheum Dis. 2016 Sep;75(9):1615-21.

Table 1

Baseline variables associated with LLDAS achievement based on multivariable Cox models

CharacteristicsModel 1Model 2Model 3HR (95% CI)pvalueHR (95% CI)pvalueHR (95% CI)pvalueAge at disease onset, years1.010 (1.003-1.016)0.0051.009 (1.002-1.016)0.0101.010 (1.003-1.017)0.004Treatment-naïve1.346 (1.105-1.641)0.0031.425 (1.161-1.749)0.0011.484 (1.204-1.830)<0.001Nephritis0.776 (0.641-0.939)0.0091.066 (0.820-1.385)0.6340.925 (0.737-1.160)0.498SLEDAI0.968 (0.950-0.987)0.001PGA0.685 (0.551-0.853)0.001Daily prednisone (or equivalent) dose, mg/d1.003 (0.998-1.007)0.2661.005 (0.999-1.010)0.093HCQ1.638 (1.263-2.123)<0.0011.713 (1.318-2.225)<0.0011.664 (1.284-2.157)<0.001

Disclosure of Interests:

None declared

Structure-Activity Relationship Studies of Pyridine-Based Ligands and Identification of a Fluorinated Derivative for Positron Emission Tomography Imaging of Cannabinoid Type 2 Receptors

The cannabinoid type 2 (CB2) receptor has emerged as a valuable target for therapy and imaging of immune-mediated pathologies. With the aim to find a suitable radiofluorinated analogue of the previously reported CB2 positron emission tomography (PET) radioligand [¹¹C]RSR-056, 38 fluorinated derivatives were synthesized and tested by in vitro binding assays. With a K_i (hCB2) of 6 nM and a selectivity factor of nearly 700 over cannabinoid type 1 receptors, target compound 3 exhibited optimal in vitro properties and was selected for evaluation as a PET radioligand. [¹⁸F]3 was obtained in an average radiochemical yield of 11 ± 4% and molar activities between 33 and 114 GBq/μmol. Specific binding of [¹⁸F]3 to CB2 was demonstrated by in vitro autoradiography and in vivo PET experiments using the CB2 ligand GW-405 833. Metabolite analysis revealed only intact [¹⁸F]3 in the rat brain. [¹⁸F]3 detected CB2 upregulation in human amyotrophic lateral sclerosis spinal cord tissue and may thus become a candidate for diagnostic use in humans.