Molecular mechanism of choline and ethanolamine transport in humans.

Human feline leukaemia virus subgroup C receptor-related proteins 1 and 2 (FLVCR1 and FLVCR2) are members of the major facilitator superfamily1. Their dysfunction is linked to several clinical disorders, including PCARP, HSAN and Fowler syndrome2-7. Earlier studies concluded that FLVCR1 may function as a haem exporter8-12, whereas FLVCR2 was suggested to act as a haem importer13, yet conclusive biochemical and detailed molecular evidence remained elusive for the function of both transporters14-16. Here, we show that FLVCR1 and FLVCR2 facilitate the transport of choline and ethanolamine across the plasma membrane, using a concentration-driven substrate translocation process. Through structural and computational analyses, we have identified distinct conformational states of FLVCRs and unravelled the coordination chemistry underlying their substrate interactions. Fully conserved tryptophan and tyrosine residues form the binding pocket of both transporters and confer selectivity for choline and ethanolamine through cation-π interactions. Our findings clarify the mechanisms of choline and ethanolamine transport by FLVCR1 and FLVCR2, enhance our comprehension of disease-associated mutations that interfere with these vital processes and shed light on the conformational dynamics of these major facilitator superfamily proteins during the transport cycle.

Omega-6 highly unsaturated fatty acids in Leydig cells facilitate male sex hormone production.

Highly unsaturated fatty acids (HUFAs) are fatty acids with more than three double bonds in the molecule. Mammalian testes contain very high levels of omega-6 HUFAs compared with other tissues. However, the metabolic and biological significance of these HUFAs in the mammalian testis is poorly understood. Here we show that Leydig cells vigorously synthesize omega-6 HUFAs to facilitate male sex hormone production. In the testis, FADS2 (Fatty acid desaturase 2), the rate-limiting enzyme for HUFA biosynthesis, is highly expressed in Leydig cells. In this study, pharmacological and genetic inhibition of FADS2 drastically reduces the production of omega-6 HUFAs and male steroid hormones in Leydig cells; this reduction is significantly rescued by supplementation with omega-6 HUFAs. Mechanistically, hormone-sensitive lipase (HSL; also called LIPE), a lipase that supplies free cholesterol for steroid hormone production, preferentially hydrolyzes HUFA-containing cholesteryl esters as substrates. Taken together, our results demonstrate that Leydig cells highly express FADS2 to facilitate male steroid hormone production by accumulating omega-6 HUFA-containing cholesteryl esters, which serve as preferred substrates for HSL. These findings unveil a previously unrecognized importance of omega-6 HUFAs in the mammalian male reproductive system.

Diagnostic performance of on-site computed CT-fractional flow reserve based on fluid structure interactions: comparison with invasive fractional flow reserve and instantaneous wave-free ratio.

AIMS: We evaluated diagnostic accuracy of CT-fractional flow reserve (CT-FFR) computed on-site with a new vendor workstation, against invasive FFR as the reference standard. METHODS AND RESULTS: Retrospective analyses compared CT-FFR of 104 vessels with 30-90% diameter stenosis in 75 patients imaged using single-rotation 320 detector-row coronary CT angiography (CCTA) with invasive FFR performed within 90 days. Prospective ECG-gated CCTA included exposure of 70-99% of the R-R interval. CT-FFR was computed on-site within the same physical space as the CT scanner and reading room. The diagnostic accuracy of CCTA >50% and CT-FFR ≤0.8 to detect hemodynamically significant stenosis, defined as FFR ≤0.8, was determined, as was the correlation of CT-FFR to FFR and instantaneous wave-free ratio (iFR). Forty-four vessels (42.3%) had an invasive FFR ≤0.8. The sensitivity, specificity, positive, and negative predictive value of CT-FFR ≤0.8 vs. CCTA >50% to detect hemodynamically significant stenosis defined as FFR ≤0.8 were 90.9% vs. 70.5%, 78.3% vs. 43.3%, 75.5% vs. 47.7%, and 92.2% vs. 66.7%, respectively. Area under the curve of CT-FFR was significantly higher than CCTA >50% [0.85, 95% confidence interval (CI): 0.76-0.91 vs. 0.57, 95% CI: 0.47-0.67; P < 0.0001]. The correlation coefficient between CT-FFR and iFR was r = 0.62 (95% CI: 0.40-0.77, P < 0.0001) and that between CT-FFR and invasive FFR was r = 0.52 (95% CI: 0.28-0.70, P = 0.0001). CT-FFR inter- and intra-observer correlations were excellent (r = 0.83 and r = 0.82, respectively). CONCLUSION: Locally computed CT-FFR based on fluid structure interaction has excellent diagnostic accuracy to detect a significant FFR ≤0.8 compared with conventional CCTA and high reproducibility.

Noninvasive Computed Tomography-Derived Fractional Flow Reserve Based on Structural and Fluid Analysis: Reproducibility of On-site Determination by Unexperienced Observers.

OBJECTIVE: The aim of this study was to evaluate the reproducibility of computed tomography (CT)-derived fractional flow reserve (FFR) determined on site by inexperienced observers using a postprocessing software based on structural and fluid analysis. METHODS: Using 21 coronary vessels in 7 patients who underwent 320-row coronary CT angiography and catheter-FFR, 2 independent inexperienced observers (A: a student radiation technologist; B: a nonmedical staff) determined the CT-FFR using a postprocessing software. After a 20-minute training session, both observers postprocessed all vessels and readjusted their settings after another training/feedback. These CT-FFRs were compared with values determined by an expert analyst. RESULTS: The mean processing times were 23 ± 4 minutes (automatic), 71 ± 5 minutes (observer A), and 57 ± 7 minutes (observer B) per patient. The initial correlations with expert data were r = 0.92 (observer A) and 0.73 (observer B) and increased to 0.83 for observer B after additional training. The final absolute difference with the expert data was 0.000 to 0.020. The correlation between catheter-FFR and expert CT-FFR was r = 0.76. CONCLUSIONS: The CT-derived FFR on-site postprocessing software showed good reproducibility for measurements by inexperienced observers.

A strategy to optimize radiation exposure for non-contrast head CT: comparison with the Japanese diagnostic reference levels.

PURPOSE: To describe how we performed a protocol review, analyzed data, identified opportunities to reduce radiation exposure, and then implemented a new imaging protocol for non-contrast adult head CT at our institution with reduced radiation exposure, using the Japanese diagnostic reference levels (DRLs) as the reference. METHODS: After analyzing the CT dose index (CTDIvol) and dose length product (DLP) in all non-contrast adult head CT examinations performed during a 3-month period (September to November 2015) in order to identify a specific protocol that contributed to the above-DRL-level radiation exposure observed for non-contrast adult head CT at our institution, phantom studies with objective and subjective image quality analyses were performed to develop a new imaging protocol. After implementing the new protocol, its feasibility was evaluated in terms of radiation exposure, prevalence of significant disease detection, and subjective image quality. RESULTS: The review of 2040 examinations revealed that a helical protocol (CTDIvol = 93.4 mGy) with one of four CT scanners mainly contributed to the above-DRL-level radiation exposure (mean DLP at this scanner = 1401.2 mGy cm) in non-contrast adult head CT at our institution. To replace this protocol, the phantom study identified a wide-volume scan using 120 kVp, 350 mAs, a 4-cm detector, a slice thickness of 5 mm, and a CTDIvol of 69.8 mGy as a new protocol that yielded comparable image quality to the existing protocol. After the implementation of the new protocol, the overall mean DLP reduced to 1365 mGy cm without any apparent degradation of image quality. No significant decrease in the prevalence of significant findings after protocol revision was noted. CONCLUSION: We report the successful implementation of a new protocol with reduced radiation exposure for non-contrast head CT examinations.