Studies on human pregnancy-induced insulin-like growth factor (IGF)-binding protein-4 proteases in serum: determination of IGF-II dependency and localization of cleavage site

Insulin-like growth factor (IGF)-binding protein-4 (IGFBP-4), a consistent inhibitor of IGF action, is subject to proteolytic cleavage by the IGF-II-dependent IGFBP-4 protease. However, regulation of the IGF-II-dependent IGFBP-4 protease in vivo is not known. As IGFBP proteases are known to be triggered during pregnancy, we systematically evaluated the changes in IGFBP-4 proteolysis by serum collected throughout human pregnancy. Results from in vitro protease assays using recombinant IGFBP-4 revealed that IGFBP-4 proteolysis determined in both the presence and absence of exogenous IGF-II significantly increased during the first and second trimesters and reached a plateau by the third trimester. However, in the absence of IGF-II, IGFBP-4 proteolysis by pregnancy serum was only observed after prolonged incubation. IGF-II dose dependently increased IGFBP-4 proteolysis by pregnancy serum, with maximal stimulation observed at a concentration of 0.7 mol/L relative to IGFBP-4. In contrast, IGF-II at an equimolar dose had little effect on proteolysis of recombinant human IGFBP-3, whereas excess IGF-II reproducibly inhibited recombinant human IGFBP-3 proteolysis by pregnancy serum. Although IGF-II enhanced IGFBP-4 proteolysis, results from N-terminal sequence and mass spectrometric analyses of IGFBP-4 proteolytic fragments demonstrate that the cleavage site (Met135-Lys136) in human IGFBP-4 was not altered by IGF-II. Deletion of the residues 121-141 containing this cleavage site blocked IGFBP-4 proteolysis. These findings demonstrate that the increase in IGFBP-4 proteolysis during pregnancy was accounted for mainly by the IGF-II-dependent IGFBP-4 proteolysis. Because IGFBP-4 is a potent inhibitor of IGF actions, it can be speculated that the pregnancy-induced IGFBP-4 proteases may play an important role in regulating fetal growth.     

The loss-of-function PCSK9Q152H variant increases ER chaperones GRP78 and GRP94 and protects against liver injury

Individuals harboring the loss-of-function (LOF) proprotein convertase subtilisin/kexin type 9 Gln152His variation (PCSK9^Q152H) have low circulating low-density lipoprotein cholesterol levels and are therefore protected against cardiovascular disease (CVD). This uncleavable form of proPCSK9, however, is retained in the endoplasmic reticulum (ER) of liver hepatocytes, where it would be expected to contribute to ER storage disease (ERSD), a heritable condition known to cause systemic ER stress and liver injury. Here, we examined liver function in members of several French-Canadian families known to carry the PCSK9^Q152H variation. We report that PCSK9^Q152H carriers exhibited marked hypocholesterolemia and normal liver function despite their lifelong state of ER PCSK9 retention. Mechanistically, hepatic overexpression of PCSK9^Q152H using adeno-associated viruses in male mice greatly increased the stability of key ER stress-response chaperones in liver hepatocytes and unexpectedly protected against ER stress and liver injury rather than inducing them. Our findings show that ER retention of PCSK9 not only reduced CVD risk in patients but may also protect against ERSD and other ER stress–driven conditions of the liver. In summary, we have uncovered a cochaperone function for PCSK9^Q152H that explains its hepatoprotective effects and generated a translational mouse model for further mechanistic insights into this clinically relevant LOF PCSK9 variant.     

Imaging Assessment of Visceral Pleural Surface Invasion by Lung Cancer: Comparison of CT and Contrast-Enhanced Radial T1-Weighted Gradient Echo 3-Tesla MRI

ObjectiveTo compare the diagnostic performance of contrast-enhanced radial T1-weighted gradient-echo 3-tesla (3T) magnetic resonance imaging (MRI) and computed tomography (CT) for the detection of visceral pleural surface invasion (VPSI). Visceral pleural invasion by non-small-cell lung cancer (NSCLC) can be classified into two types: PL1 (without VPSI), invasion of the elastic layer of the visceral pleura without reaching the visceral pleural surface, and PL2 (with VPSI), full invasion of the visceral pleura.Materials and MethodsThirty-three patients with pathologically confirmed VPSI by NSCLC were retrospectively reviewed. Multidetector CT and contrast-enhanced 3T MRI with a free-breathing radial three-dimensional fat-suppressed volumetric interpolated breath-hold examination (VIBE) pulse sequence were compared in terms of the length of contact, angle of mass margin, and arch distance-to-maximum tumor diameter ratio. Supplemental evaluation of the tumor-pleura interface (smooth versus irregular) could only be performed with MRI (not discernible on CT).ResultsAt the tumor-pleura interface, radial VIBE MRI revealed a smooth margin in 20 of 21 patients without VPSI and an irregular margin in 10 of 12 patients with VPSI, yielding an accuracy, sensitivity, specificity, positive predictive value, negative predictive value, and F-score for VPSI detection of 91%, 83%, 95%, 91%, 91%, and 87%, respectively. The McNemar test and receiver operating characteristics curve analysis revealed no significant differences between the diagnostic accuracies of CT and MRI for evaluating the contact length, angle of mass margin, or arch distance-to-maximum tumor diameter ratio as predictors of VPSI.ConclusionThe diagnostic performance of contrast-enhanced radial T1-weighted gradient-echo 3T MRI and CT were equal in terms of the contact length, angle of mass margin, and arch distance-to-maximum tumor diameter ratio. The advantage of MRI is its clear depiction of the tumor-pleura interface margin, facilitating VPSI detection.     

Clinical Outcomes of Large (>10 mm) Unruptured Posterior Circulation Aneurysms and Their Predictors

ObjectiveThe treatment of large aneurysms of the posterior circulation is complicated and remains challenging. We here analyzed our institutional clinical outcomes of large unruptured aneurysms of the posterior circulation. MethodsThis study included 56 patients who presented with a large (>10 mm) unruptured aneurysm of the posterior circulation between 2002 and 2018. ResultsThere were 18 (32.1%) male and 38 (67.9%) female patients, with a mean age of 53.4 years. The most common location was the vertebral artery, followed by the basilar tip and posterior cerebral artery. The median follow-up duration was 29 months. Eighteen patients (32.1%) were treated by transcranial surgery and 38 (67.9%) were treated by endovascular treatment (EVT). Posttreatment complications occurred in 16 patients (28.6%), with there being no significant difference between the transcranial surgery and EVT groups. Complete obliteration was achieved in 30 patients (53.6%), with there being no statistically significant difference between the transcranial surgery and EVT groups. Recurrence occurred in 17 patients (30.4%), and the rate of recurrence was higher in the EVT group than in the transcranial surgery group (39.5% vs. 11.1%, p=0.03). Forty-four (84%) of 56 patients showed a favorable functional outcome. In saccular aneurysm, EVT was negative predictor of worsening of functional status. ConclusionTreatment of these aneurysms harbors an inherent high risk of morbidity. No superiority was found between transcranial surgery and EVT in terms of complications and complete obliteration, but transcranial surgery showed a higher treatment durability than EVT.