Left ventricular reverse remodeling following initiation of sacubitril/valsartan for heart failure with reduced ejection fraction and low blood pressure.

Sacubitril/valsartan has become an important first-line drug for symptomatic heart failure (HF) patients, especially with left ventricular (LV) ejection fraction (LVEF) < 50%. However, the impact of sacubitril/valsartan on cardiovascular outcomes, especially LV reverse remodeling for such patients with low blood pressure, remains uncertain. We retrospectively studied 164 HF patients with LVEF < 50% who were treated with sacubitril/valsartan from two institutions. Echocardiography was performed before and 9.5 ± 5.1 months after initiation of maximum tolerated dose of sacubitril/valsartan. The maximum tolerated dose of sacubitril/valsartan was lower for the low blood pressure group (≤ 100 mmHg in systole) than for the non-low blood pressure group (> 100 mmHg in systole) (165 ± 106 mg vs. 238 ± 124 mg, P = 0.017). As expected, significant LV reverse remodeling was observed in the non-low blood pressure group after initiation of sacubitril/valsartan. It was noteworthy that significant LV reverse remodeling was also observed in the low blood pressure group after initiation of sacubitril/valsartan (LV end-diastolic volume: 177.3 ± 66.0 mL vs. 137.7 ± 56.1 mL, P < 0.001, LV end-systolic volume: 131.6 ± 60.3 mL vs. 94.6 ± 55.7 mL, P < 0.001, LVEF: 26.8 ± 10.3% vs. 33.8 ± 13.6%, P = 0.015). Relative changes in LV volumes and LVEF after initiation of sacubitril/valsartan were similar for the two groups. In conclusion, significant LV reverse remodeling occurred after initiation of sacubitril/valsartan, even in HF patients with LVEF < 50% and systolic blood pressure ≤ 100 mmHg.

Impact of Tafamidis on Echocardiographic Cardiac Function of Patients With Transthyretin Cardiac Amyloidosis.

BACKGROUND: The efficacy of a therapy for patients with transthyretin amyloid cardiomyopathy (ATTR-CM) has not been proven, but tafamidis has been associated with favorable outcomes. However, echocardiographic details of the association of tafamidis with cardiac morphology remain undetermined. Moreover, whether the efficacy of tafamidis varies with the degree of cardiac involvement remains unknown. Using echocardiography, this study investigated the impact of tafamidis on the cardiac morphology of patients with ATTR-CM.Methods and Results: Of 52 consecutive patients with biopsy-proven ATTR-CM at Kobe University Hospital, we included 41 for whom details of follow-up echocardiographic examinations after the administration of tafamidis were available. All patients underwent standard and speckle-tracking echocardiography before and a mean (±SD) of 16±8 months after the administration of tafamidis. No significant changes were observed in any representative echocardiographic parameters after the administration of tafamidis. Furthermore, there were no significant changes observed in subgroup analyses (e.g., left ventricular [LV] ejection fraction ≥50% vs. <50%; LV mass index <150 vs. ≥150 g/m2; New York Heart Association Class I-II vs. Class III; age ≥80 vs. <80 years). CONCLUSIONS: Tafamidis may prevent worsening of various representative echocardiographic parameters of patients with ATTR-CM. This effect is also seen in patients with relatively advanced disease and in those who are elderly.

Identification of factors associated with progression of left atrial enlargement in patients with atrial fibrillation.

Left atrial (LA) enlargement frequently occurs in atrial fibrillation (AF) patients, and this enlargement is associated with the development of heart failure, thromboembolism, or atrial functional mitral regurgitation (AFMR). AF patients can develop LA enlargement over time, but its progression depends on the individual. So far, the factors that cause progressive LA enlargement in AF patients have thus not been elucidated, so that the aim of this study was to identify the factors associated with the progression of LA enlargement in AF patients. We studied 100 patients with persistent or permanent AF (aged: 67 ± 2 years, 40 females). Echocardiography was performed at baseline and 12 (5-30) months after follow-up. LA size was evaluated as the LA volume index which was calculated with the biplane modified Simpson's method from apical four-and two-chamber views, and then normalized to the body surface area (LAVI). The deterioration of AFMR after follow-up was defined as a deterioration in severity of mitral regurgitation (MR) by a grade of 1 or more. Multivariate regression analysis demonstrated that hypertension (p = .03) was an independently associated parameter of progressive LA enlargement, as was baseline LAVI. In addition, the Kaplan-Meier curve indicated that patients with hypertension tended to show greater deterioration of AFMR after follow-up than those without hypertension (log-rank p = .08). Hypertension proved to be strongly associated with progression of LA enlargement over time in patients with AF. Our findings provide new insights for better management of patients with AF to prevent the development of AFMR.

Pharmacokinetics and effect of maslinic acid with physical exercise on grip strength and trunk muscle mass in healthy Japanese individuals.

Age-related changes in physical function are closely associated with daily activity impairment among the elderly. Continuous maslinic acid intake may improve skeletal muscle mass; however, the concentration-dependent benefits of maslinic acid for physical functionality remain unclear. Therefore, we evaluated the bioavailability of maslinic acid and examined the effect of maslinic acid intake on skeletal muscle and quality of life in the healthy Japanese elderly. Five healthy adult men were administered test diets containing 30, 60, or 120 mg of maslinic acid. Analysis of plasma maslinic acid revealed concentration-dependent elevations in blood maslinic acid levels (p<0.01). Next, 69 healthy Japanese adult men and women were administered a placebo or 30 or 60 mg of maslinic acid continuously for 12 weeks with physical exercise in a randomized, double-blind, placebo-controlled trial. The trunk muscle mass (p<0.05) and vitality score according to the Short-Form-8 (p<0.05) were significantly higher in the 60 mg maslinic acid group than in the placebo group. Additionally, grip strength was significantly higher in the 30 (p<0.05) and 60 mg (p<0.05) groups than in the placebo group. Overall, maslinic acid intake with physical exercise improved muscle strength, muscle mass, and quality of life in a maslinic acid-intake-dependent manner.

Glucokinase activation leads to an unsustained hypoglycaemic effect with hepatic triglyceride accumulation in db/db mice.

AIM: To investigate how subchronic administration of a glucokinase activator (GKA) results in attenuation of the hypoglycaemic effect in the diabetic condition. MATERIALS AND METHODS: Six-week-old db/db mice were fed standard chow containing a GKA or the sodium-glucose cotransporter 2 inhibitor ipragliflozin for 1, 6, 14 or 28 days. We performed histological evaluation and gene expression analysis of the pancreatic islets and liver after each treatment and compared the results to those in untreated mice. RESULTS: The unsustained hypoglycaemic effect of GKAs was reproduced in db/db mice in conjunction with significant hepatic fat accumulation. The initial reactions to treatment with the GKA in the liver were upregulation of the gene expression of carbohydrate response element-binding protein beta (Chrebp-b) and downregulation of phosphoenolpyruvate carboxykinase (Pepck) on day 1. Subsequently, the initial changes in Chrebp-b and Pepck disappeared and increases in the expression of genes involved in lipogenesis, including acetyl-CoA carboxylase and fatty acid synthase, were observed. There were no significant changes in the pancreatic ß cells nor in hepatic insulin signalling. CONCLUSIONS: The GKA showed an unsustained hypoglycaemic effect and promoted hepatic fat accumulation in db/db mice. Dynamic changes in the expression of hepatic genes involved in lipogenesis and gluconeogenesis could affect the unsustained hypoglycaemic effect of the GKA despite no changes in pancreatic ß-cell function and mass.

Effect of heart rate on left ventricular longitudinal myocardial function in type 2 diabetes mellitus.

BACKGROUND: Left ventricular (LV) longitudinal myocardial dysfunction is considered a marker of preclinical LV dysfunction in patients with type 2 diabetes mellitus (T2DM). High heart rate (HR) is associated with cardiovascular outcomes, but the effect of HR on LV longitudinal myocardial function in T2DM patients is uncertain. METHODS: We studied 192 T2DM patients with preserved LV ejection fraction (LVEF), and 81 age-, sex-, and LVEF-matched healthy volunteers. HR was measured as the average HR during echocardiography, and high HR was defined as resting HR ≥ 70 beats/minute. LV longitudinal myocardial function was assessed as global longitudinal strain (GLS). The predefined cutoff for subclinical LV dysfunction was set at GLS < 18%. RESULTS: GLS in T2DM patients with high HR was significantly lower than that in T2DM patients with low HR (16.3% ± 4.2% vs. 17.8% ± 2.8%; P = 0.03), whereas GLS in normal subjects with high and low HR was similar (20.3 ± 1.7% vs. 20.3 ± 2.0%; P = 0.99). Multivariable logistic regression analysis showed that high HR (odds ratio: 1.04; 95% confidence interval: 1.01-1.07; P = 0.01) was independently associated with GLS < 18% in T2DM patients as well as HbA1c, T2DM duration, LVEF, body mass index, and mitral inflow E and mitral e' annular velocity ratio. One sequential logistic model evaluating the associations between GLS < 18% and clinical variables in T2DM patients showed an improvement with the addition of LVEF and E/e' (P < 0.001) and a further improvement with the addition of high HR (P < 0.001). CONCLUSION: Compared with normal subjects, resting HR was associated with LV longitudinal myocardial function in asymptomatic T2DM patients with preserved LVEF. Our findings provide new insights on the management of T2DM patients.

Association of left ventricular longitudinal myocardial function with subclinical right ventricular dysfunction in type 2 diabetes mellitus.

BACKGROUND: Left ventricular (LV) involvement in diabetic cardiomyopathy has been reported; however, only limited data exist on right ventricular (RV) involvement. Therefore, our purpose was to investigate RV systolic dysfunction and its association with LV longitudinal myocardial dysfunction in patients with type 2 diabetes mellitus (T2DM) and preserved LV ejection fraction (LVEF). METHODS: We studied 177 T2DM patients with preserved LVEF and 79 age-, sex-, and LVEF-matched healthy volunteers. LV longitudinal myocardial function was assessed as global longitudinal strain (GLS), and RV systolic function was assessed as RV free-wall strain, and predefined cutoff values for subclinical dysfunction were set at GLS < 18% and RV free-wall strain < 20%, respectively. RESULTS: RV free-wall strain in T2DM patients was significantly lower than that in normal controls (19.3% ± 4.8% vs. 24.4% ± 5.1%; P < 0.0001). RV free-wall strain in T2DM patients and LV longitudinal dysfunction was similar compared to that in T2DM patients without (19.0 ± 4.5% vs. 19.6 ± 5.0%, P = 0.40). Furthermore, multivariate logistic regression analyses showed that GLS was independently associated with RV systolic dysfunction as well as mitral inflow E and mitral e' annular velocities ratio (odds ratio, 1.16; 95% confidence interval: 1.03-1.31; P < 0.05). Sequential logistic models evaluating the association of RV systolic dysfunction in T2DM patients showed an improvement in clinical variables (χ2 = 6.2) with the addition of conventional echocardiographic parameters (χ2 = 13.4, P < 0.001) and a further improvement with the addition of GLS (χ2 = 20.8, P < 0.001). CONCLUSION: RV subclinical systolic dysfunction was observed in T2DM patients with preserved LVEF and was associated with LV longitudinal myocardial dysfunction. Our findings may provide additional findings for the management of T2DM patients.

Severe infection including disseminated herpes zoster triggered by subclinical Cushing's disease: a case report.

BACKGROUND: Subclinical Cushing's disease (SCD) is defined by corticotroph adenoma-induced mild hypercortisolism without typical physical features of Cushing's disease. Infection is an important complication associated with mortality in Cushing's disease, while no reports on infection in SCD are available. To make clinicians aware of the risk of infection in SCD, we report a case of SCD with disseminated herpes zoster (DHZ) with the mortal outcome. CASE PRESENTATION: An 83-year-old Japanese woman was diagnosed with SCD, treated with cabergoline in the outpatient. She was hospitalized for acute pyelonephritis, and her fever gradually resolved with antibiotics. However, herpes zoster appeared on her chest, and the eruptions rapidly spread over the body. She suddenly went into cardiopulmonary arrest and died. Autopsy demonstrated adrenocorticotropic hormone-positive pituitary adenoma, renal abscess, and DHZ. CONCLUSIONS: As immunosuppression caused by SCD may be one of the triggers of severe infection, the patients with SCD should be assessed not only for the metabolic but also for the immunodeficient status.

Maslinic acid activates mTORC1 and human TGR5 and induces skeletal muscle hypertrophy.

Maslinic acid, a naturally occurring pentacyclic triterpene in more than 30 plants (including olives), reportedly increases human muscle mass and muscle strength; however, the underlying molecular mechanism remains unknown. C57BL/6J mice were fed a standard diet or supplemented with 0.27% maslinic acid for 4 weeks, and their skeletal muscle mass was measured. Mice that consumed maslinic acid displayed significant increases in gastrocnemius and soleus muscle mass. Cultured mouse-C2C12 skeletal muscle cells were treated with mammalian target of rapamycin complex 1 (mTORC1) or protein kinase b (Akt) inhibitor, and protein synthesis was quantified. Maslinic acid accelerated protein synthesis via mTORC1 activation independent of Akt. Furthermore, maslinic acid activated human Takeda G protein-coupled receptor 5 (TGR5) more strongly than mouse TGR5, augmenting the expression of several genes related to muscular hypertrophy. Maslinic acid activated mTORC1 and human TGR5, implying its contribution to human muscular hypertrophy through these effects.

Self-Perception of the Knee Is Associated with Joint Motion during the Loading Response in Individuals with Knee Osteoarthritis: A Pilot Cross-Sectional Study.

Small knee flexion motion is a characteristic of gait in individuals with knee osteoarthritis. This study examined the relationship between knee flexion excursion in loading response and knee self-perception in individuals with knee osteoarthritis. Twenty-one individuals with knee osteoarthritis participated in this study. Knee flexion excursions in loading response while walking at a comfortable and a fast-walking speed were measured using an inertial measurement unit-based motion capture system. The degree of knee perceptual impairment was evaluated using the Fremantle Knee Awareness Questionnaire (FreKAQ). The relationships between the FreKAQ score and gait variables and knee function were evaluated by calculating the correlation coefficient. The unique contributions of knee self-perception and muscle strength to knee flexion excursion in loading response were analyzed using hierarchical linear regression. Knee self-perception was significantly correlated with pain during walking, muscle strength and knee flexion excursion at fast speed. In the fast speed condition only, impaired knee self-perception was inversely proportional to knee flexion excursion and accounted for 21.8% of the variance in knee flexion excursion. This result suggests that impaired self-perception of the knee may help to explain the decrease in the knee flexion excursion in the loading response in individuals with knee osteoarthritis.

A secreted decoy of InR antagonizes insulin/IGF signaling to restrict body growth in Drosophila.

Members of the insulin peptide family have conserved roles in the regulation of growth and metabolism in a wide variety of metazoans. Drosophila insulin-like peptides (Dilps) promote tissue growth through the single insulin-like receptor (InR). Despite the important role of Dilps in nutrient-dependent growth control, the molecular mechanism that regulates the activity of circulating Dilps is not well understood. Here, we report the function of a novel secreted decoy of InR (SDR) as a negative regulator of insulin signaling. SDR is predominantly expressed in glia and is secreted into the hemolymph. Larvae lacking SDR grow at a faster rate, thereby increasing adult body size. Conversely, overexpression of SDR reduces body growth non-cell-autonomously. SDR is structurally similar to the extracellular domain of InR and interacts with several Dilps in vitro independent of Imp-L2, the ortholog of the mammalian insulin-like growth factor-binding protein 7 (IGFBP7). We further demonstrate that SDR is constantly secreted into the hemolymph independent of nutritional status and is essential for adjusting insulin signaling under adverse food conditions. We propose that Drosophila uses a secreted decoy to fine-tune systemic growth against fluctuations of circulating insulin levels.

Factors with remission of fatty liver in patients with type 2 diabetes treated with ipragliflozin.

We investigated the factors associated with fatty liver remission via treatment with ipragliflozin. The analysis was obtained from our multi-center prospective observational study, including 200 Japanese patients with type 2 diabetes treated with ipragliflozin (50 mg/day) for 24 weeks. The extent of fatty liver was estimated using a fatty liver index (FLI). Based on the FLI after the treatment with ipragliflozin, patients were classified into remission group (FLI < 30) and non-remission group (FLI ≥ 30). After treatment with ipragliflozin for 24 weeks, FLI significantly improved from 64.5 ± 21.6 to 51.9 ± 26.5 (p < 0.01). Body weight, body mass index, waist circumference, aspartate aminotransferase, alanine aminotransferase, and FLI in the remission group were significantly lower compared with those of the non-remission group. Stepwise analysis showed that the baseline FLI (Odds ratio 0.86; 95% confidence interval 0.81-0.90, p < 0.01) was an independent factor associated with FLI remission. Using a receiver operating characteristic (ROC) analysis, the adequate cut-off value for the remission was 50. The area under the ROC curve was 0.93 with the sensitivity and specificity 84.6% and 90.1% respectively. In conclusion, ipragliflozin ameliorated fatty liver. These results suggest that patients with fatty liver with a lower FLI are more likely to attain remission by the treatment with ipragliflozin.

Longitudinal morphological change of acetabular subchondral bone cyst after total hip arthroplasty in developmental dysplasia of the hip.

PURPOSE: The purpose of this study is to clarify morphological changes of acetabular subchondral bone cyst after total hip arthroplasty for osteoarthritis secondary to developmental dysplasia of the hip. METHODS: Two hundred and sixty-one primary cementless total hip arthroplasties of 208 patients, 18 males, 190 females, were retrospectively reviewed. Morphological changes of subchondral bone cyst were evaluated by computed tomography (CT). The mean cross-sectional area of the cyst from CT scans at 3 months postoperatively and after 7-10 years (average 8.4 years) were compared. RESULTS: Acetabular subchondral bone cysts were found in 49.0% of all cases in preoperative CT scans. There was no cyst which was newly recognized in CT scan performed after postoperative 7-10 years. All the cross-sectional areas of the cysts evaluated in this study were reduced postoperatively. CONCLUSIONS: This study revealed that acetabular subchondral bone cysts do not increase or expand after total hip arthroplasty and indicated that the longitudinal morphological change of acetabular bone cysts in patients of developmental dysplasia of the hip do not influence long-term implant fixation in total hip arthroplasty.

Comparison of Bone Remodeling Between an Anatomic Short Stem and a Straight Stem in 1-Stage Bilateral Total Hip Arthroplasty.

BACKGROUND: Femurs of dysplastic hips exhibit specific abnormalities, and use of modular or specially designed components is recommended. An anatomic short stem was previously designed specifically for dysplastic hips using 3-dimensional data acquired from dysplastic patients. To investigate effects of stem geometry on bone remodeling, we undertook a prospective, randomized study of patients who had undergone 1-stage bilateral total hip arthroplasty (THA) with the anatomic short stem on one side and a conventional straight stem on the other. METHODS: The study included 36 patients who underwent the above THA procedure. We assessed bone mineral density as well as the presence of cancellous condensation or bony atrophy due to stress shielding based on the analysis of Gruen's zones and newly defined equal-interval zones, at an average follow-up period of 9.2 years. RESULTS: All stems were bone ingrown stable. Cancellous condensation was observed more proximally, and areas of bone atrophy were narrower on the anatomic short stem side than on the straight stem side. Bone mineral density values reflected results of cancellous condensation and stress shielding and were higher in more proximal zones on the anatomic short stem side than on the straight stem side. CONCLUSION: Although radiographic results indicated good midterm outcomes of THA with both stems, the loading pattern differed. The anatomic short stem achieved its design purpose in terms of proximal fixation and load transfer and led to better preservation of the proximal femur.

Pathogenicity of IgG in patients with IgG4-related disease.

OBJECTIVE: IgG4-related disease (IgG4-RD) is a systemic disease characterised by elevated serum IgG4 and IgG4-positive lymphoplasmacytic infiltration in the affected tissues. The pathogenic role of IgGs, including IgG4, in patients with IgG4-RD, however, is unknown. DESIGN: We examined the pathogenic activity of circulating IgGs in patients with IgG4-RD by injecting their IgGs into neonatal male Balb/c mice. Binding of patient IgGs to pancreatic tissue was also analysed in an ex vivo mouse organ culture model and in tissue samples from patients with autoimmune pancreatitis (AIP). RESULTS: Subcutaneous injection of patient IgG, but not control IgG, resulted in pancreatic and salivary gland injuries. Pancreatic injury was also induced by injecting patient IgG1 or IgG4, with more destructive changes induced by IgG1 than by IgG4. The potent pathogenic activity of patient IgG1 was significantly inhibited by simultaneous injection of patient IgG4. Binding of patient IgG, especially IgG1 and IgG4, to pancreatic tissue was confirmed in both the mouse model and AIP tissue samples. CONCLUSIONS: IgG1 and IgG4 from patients with IgG4-RD have pathogenic activities through binding affected tissues in neonatal mice.

Limited significance of screening computed tomography after cementless total hip arthroplasty with highly cross-linked polyethylene at 7-10 years of follow-up.

OBJECTIVES: The purpose of this retrospective study is to report the incidence of osteolysis and evaluate the significance of screening computed tomography (CT) compared to plain radiography in detecting osteolysis after total hip arthroplasty with metal-on-highly cross-linked polyethylene bearings. METHODS: We retrospectively reviewed 264 primary cementless total hip arthroplasties of 211 patients, 24 males, 187 females, who received postoperative screening CT scan in addition to radiography at postoperative 7-10 years (average 8.2 years). First-generation highly cross-linked polyethylene was used in all cases. RESULTS: On the plain radiographs, no acetabular osteolysis (0%) and two cases of femoral osteolysis (0.8%) were found in the follow-up period. No osteolysis was newly found by screening CT scan. CONCLUSIONS: Very low incidence of osteolysis after total hip arthroplasty with highly cross-linked polyethylene at postoperative 7-10 years was confirmed, and routine screening CT scan for detecting osteolysis in this setting was not supported from this study.

Comparison of Different Materials and Proximal Coatings Used for Femoral Components in One-Stage Bilateral Total Hip Arthroplasty.

To evaluate the mid-term effects of different materials and coatings used for femoral components, we prospectively performed 21 one-stage bilateral total hip arthroplasties using 2 anatomical stems which have identical geometries, randomized to side. One stem was made of Ti6Al4V alloy and had a hydroxyapatite coating on grit-blasted surface proximally, and the other was made of TMZF™ alloy and had a proximal coating of hydroxyapatite in addition to an arc-deposited titanium surface coating. Although we found extensions of radiopaque lines to the surface of coatings of seven grit-blasted stems whereas we found none in the case of the arc-deposited titanium stems, all hips showed excellent clinical and radiological outcomes as shown by radiographs and bone mineral density at the final follow-up, average 5.5 years postoperatively.

The association between maternal insulin resistance in mid-pregnancy and neonatal birthweight in uncomplicated pregnancies.

There have been few studies performed to address the association between the degree of physiological increase in maternal insulin resistance during pregnancy and neonatal birthweight in non-diabetic pregnancy. We attempted to determine whether maternal insulin resistance, as measured by homeostasis model assessment-insulin resistance (HOMA-IR), in mid-pregnancy is associated with neonatal birthweight in normal pregnancies. In this retrospective observational study, we measured HOMA-IR in singleton healthy pregnant women who underwent a 75 g oral glucose tolerance test (OGTT) in mid-pregnancy because of a positive diabetes screen. Using multivariate analyses to adjust for maternal parity, pre-gestational obesity, gestational weight gain, plasma glucose levels, and gestational age at delivery, we tested the association between HOMA-IR and birthweight in their offspring. We also tested the association HOMA-IR and a risk of large-for-gestational-age (LGA) infants. In 655 Japanese women, HOMA-IR was positively associated with birthweight after adjusting for these confounders (p<0.05). A higher HOMA-IR was significantly associated with an increased incidence of LGA infants with an adjusted odds ratio of 1.53 (95% confidence interval, 1.10-2.15) per 1 unit of HOMA-IR. The degree of maternal insulin resistance in mid-pregnancy was associated with birthweight and the risk of giving birth to an LGA infant in normal pregnancies, independent of maternal obesity and glucose levels.

Detection of Active SARS-CoV-2 3CL Protease in Infected Cells Using Activity-Based Probes with a 2,6-Dichlorobenzoyloxymethyl Ketone Reactive Warhead.

The 3CL protease (3CLpro) is a viral cysteine protease of SARS-CoV-2 and is responsible for the main processing of the viral polyproteins involved in viral replication and proliferation. Despite the importance of 3CLpro as a drug target, the intracellular dynamics of active 3CLpro, including its expression and subcellular localization in SARS-CoV-2-infected cells, are poorly understood. Herein, we report an activity-based probe (ABP) with a clickable alkyne and an irreversible warhead for the SARS-CoV-2 3CL protease. We designed and synthesized two ABPs that contain a chloromethyl ketone (probe 2) or 2,6-dichlorobenzoyloxymethyl ketone (probe 3) reactive group at the P1' site. Labeling of recombinant 3CLpro by the ABPs in the purified and proteome systems revealed that probe 3 displayed ligand-directed and selective labeling against 3CLpro. Labeling of transiently expressed active 3CLpro in COS-7 cells also validated the good target selectivity of probe 3 for 3CLpro. We finally demonstrated that endogenously expressed 3CLpro in SARS-CoV-2-infected cells can be detected by fluorescence microscopy imaging using probe 3, suggesting that active 3CLpro at 5 h postinfection is localized in the juxtanuclear region. To the best of our knowledge, this is the first report investigating the subcellular localization of active 3CLpro by using ABPs. We believe that probe 3 will be a useful chemical tool for acquiring important biological knowledge of active 3CLpro in SARS-CoV-2-infected cells.