Arthi Kumaravel

Hepatic sortilin regulates both apolipoprotein B secretion and LDL catabolism

Genome-wide association studies (GWAS) have identified a genetic variant at a locus on chromosome 1p13 that is associated with reduced risk of myocardial infarction, reduced plasma levels of LDL cholesterol (LDL-C), and markedly increased expression of the gene sortilin-1 (SORT1) in liver. Sortilin is a lysosomal sorting protein that binds ligands both in the Golgi apparatus and at the plasma membrane and traffics them to the lysosome. We previously reported that increased hepatic sortilin expression in mice reduced plasma LDL-C levels. Here we show that increased hepatic sortilin not only reduced hepatic apolipoprotein B (APOB) secretion, but also increased LDL catabolism, and that both effects were dependent on intact lysosomal targeting. Loss-of-function studies demonstrated that sortilin serves as a bona fide receptor for LDL in vivo in mice. Our data are consistent with a model in which increased hepatic sortilin binds intracellular APOB-containing particles in the Golgi apparatus as well as extracellular LDL at the plasma membrane and traffics them to the lysosome for degradation. We thus provide functional evidence that genetically increased hepatic sortilin expression both reduces hepatic APOB secretion and increases LDL catabolism, providing dual mechanisms for the very strong association between increased hepatic sortilin expression and reduced plasma LDL-C levels in humans.

Indications and Techniques for Endoscopic Submucosal Dissection

Endoscopic submucosal dissection (ESD) allows for curative resection of superficial neoplasms of the gastrointestinal tract. Although ESD is the standard of care in Japan, its adoption in the West has been slow. Recent studies have shown the advantages of ESD over endoscopic mucosal resection, and as many of the barriers to ESD have been overcome, we are seeing an increasing interest in this technique. ESD can be used to treat superficial gastric, esophageal, and colorectal lesions. The most important pre-procedure step is estimating the depth of invasion of a lesion and by proxy the risk of lymph node metastasis. After a lesion has been resected, the histopathological analysis will determine whether the resection was curative or whether further surgery is needed. In conclusion, ESD is being more widely used in the West, and it is important to understand the indications, limitations, and techniques of ESD.

Diagnosis of Celiac Disease in Adults Based on Serology Test Results, Without Small-Bowel Biopsy

BACKGROUND & AIMS Celiac disease is underdiagnosed, with nonspecific symptoms and high morbidity. New diagnostic factors are needed. We aimed to estimate the frequency at which adult patients with positive results from serology tests are referred for small-bowel biopsies and to identify factors that improve the diagnosis of celiac disease. METHODS We performed a retrospective analysis of data from 2477 subjects who received serology tests for celiac disease between 2005 and 2007. We analyzed results for total levels of IgA, IgA against human tissue transglutaminase (hTTG), IgA and IgG against gliadin, as well as dilution titers of IgA against endomysial antibodies (EMA). Biopsy samples were analyzed by pathologists experienced in detecting mucosal changes associated with celiac disease and graded according to the Marsh system. RESULTS Of the 2477 patients, 610 (25%) had abnormal results from serology tests, and 39% of these patients (240 of 610) underwent small-bowel biopsy analyses. Of these patients, 50 (21%) had biopsy findings consistent with celiac disease (Marsh 3 lesions) and were placed on gluten-free diets. Titers of IgA hTTG greater than 118 U identified patients with celiac disease with a 2% false-positive rate. Titers of 21 to 118 U, in combination with an EMA dilution titer of 1:160 or greater, had a positive predictive value of 83% for celiac disease. IgA hTTG levels less than 20 U, in combination with an EMA dilution titer less than 1:10, had a negative predictive value of 92% for celiac disease. CONCLUSIONS Serum levels of IgA hTTG greater than 118 U, or 21 to 118 U in combination with an EMA dilution titer of 1:160 or greater, can be used to identify adult symptomatic patients with celiac disease, in the absence of a small-bowel biopsy.

Brush cytology vs. endoscopic biopsy for the surveillance of Barrett's esophagus.

BACKGROUND AND STUDY AIMS Periodic surveillance with systematic biopsies is recommended for patients with Barretts esophagus. Brush cytology has been proposed as a simple inexpensive component of endoscopic surveillance, which may also detect abnormalities prior to detection of histologic abnormalities. The aim of the current study was to determine whether brush cytology provides any additional value over endoscopic surveillance biopsies in patients with Barretts esophagus. PATIENTS This retrospective cohort study included 530 patients with Barretts esophagus undergoing endoscopic surveillance with paired biopsy and cytology specimens at the Cleveland Clinic between January 1994 and July 2008. The main outcome measures were sensitivity, specificity, and concordance rates of cytology and histology. RESULTS Sensitivity of cytology for any dysplasia was 49 % and specificity was 95 %. However, sensitivity was 82 % for detection of high grade dysplasia/adenocarcinoma but only 31 % for low grade/indefinite for dysplasia. The concordance rate between cytology and histology was 80 %. Histology had a higher dysplasia detection rate than cytology (24.0 % vs. 15.7 %, respectively; P <0.0001). CONCLUSIONS Cytology has excellent specificity and good sensitivity for the detection of high grade dysplasia/adenocarcinoma but poor sensitivity for low grade dysplasia. There was substantial concordance between cytology and histology for the detection of dysplasia. However, histology had a higher dysplasia detection rate and therefore the value of routine cytology in the surveillance of Barretts esophagus is questionable.

The effects of apolipoprotein F deficiency on high density lipoprotein cholesterol metabolism in mice.

Apolipoprotein F (apoF) is 29 kilodalton secreted sialoglycoprotein that resides on the HDL and LDL fractions of human plasma. Human ApoF is also known as Lipid Transfer Inhibitor protein (LTIP) based on its ability to inhibit cholesteryl ester transfer protein (CETP)-mediated transfer events between lipoproteins. In contrast to other apolipoproteins, ApoF is predicted to lack strong amphipathic alpha helices and its true physiological function remains unknown. We previously showed that overexpression of Apolipoprotein F in mice reduced HDL cholesterol levels by 20–25% by accelerating clearance from the circulation. In order to investigate the effect of physiological levels of ApoF expression on HDL cholesterol metabolism, we generated ApoF deficient mice. Unexpectedly, deletion of ApoF had no substantial impact on plasma lipid concentrations, HDL size, lipid or protein composition. Sex-specific differences were observed in hepatic cholesterol content as well as serum cholesterol efflux capacity. Female ApoF KO mice had increased liver cholesteryl ester content relative to wild type controls on a chow diet (KO: 3.4+/−0.9 mg/dl vs. WT: 1.2+/−0.3 mg/dl, p<0.05). No differences were observed in ABCG1-mediated cholesterol efflux capacity in either sex. Interestingly, ApoB-depleted serum from male KO mice was less effective at promoting ABCA1-mediated cholesterol efflux from J774 macrophages relative to WT controls.

Video-based supervision for training of endoscopic submucosal dissection

BACKGROUND AND STUDY AIM Adoption of endoscopic submucosal dissection (ESD) in Western countries has been limited by the difficulty in learning the procedure. Although a porcine model is commonly used for ESD training, without expert guidance the procedure is difficult to master. The availability of Western ESD experts is limited, and expert supervision through a remote video-based system may be a practical method for Western endoscopists to learn ESD. The aim of this study was to assess the value of video-based remote evaluation in supervising ESD training. METHODS Two Western endoscopists performed ESD training procedures in an ex vivo porcine model at least every 2 weeks until competency was achieved. Competency was defined as consistent en bloc resection of a 3-cm area within 30 minutes, and without perforation, using the proper ESD technique. A Japanese ESD expert at the National Cancer Center in Tokyo, Japan, analyzed the training videos, scored them, and provided written feedback for improvement after each training session and before the trainees next training session. RESULTS Endoscopist 1 reached competency at 23 procedures and endoscopist 2 reached competency at 25 procedures. No difference in skill improvement between the two endoscopists was noted. One trainee subsequently completed eight ESD procedures in patients, with curative en bloc resection and no complications. CONCLUSION A standardized ESD training program including educational presentations/videos and preclinical animal training with expert guidance through a remote video-based system is an effective tool for learning ESD techniques in preparation for performing the procedure in humans.

Volatile organic compounds in plasma for the diagnosis of esophageal adenocarcinoma: a pilot study.

BACKGROUND AND AIMS A noninvasive screening test that can detect esophageal adenocarcinoma (EAC) at an earlier stage could improve the prognosis associated with EAC. The role of plasma volatile organic compounds (VOCs) for the diagnosis of EAC has not been previously studied. METHODS Plasma samples were collected from subjects with EAC and GERD before endoscopy. Twenty-two preselected VOCs were analyzed with selected ion flow tube mass spectrometry. RESULTS The headspaces from 39 plasma samples (20 EAC, 19 GERD) were analyzed. The levels of 9 VOCs (acetonitrile, acrylonitrile, carbon disulfide, isoprene, 1-heptene, 3-methylhexane, [E]-2-nonene, hydrogen sulfide, and triethylamine) were significantly altered in EAC patients compared with GERD patients. A multivariable logistic regression analysis was performed to build a model for the prediction of EAC. The model identified patients with EAC with an area under the curve of 0.83 (95% confidence interval, 0.67-0.98). CONCLUSIONS Plasma VOCs may be useful in diagnosing EAC. Larger studies are needed to confirm our pilot study observations.

Deletion of murine Arv1 results in a lean phenotype with increased energy expenditure.

Background:ACAT-related enzyme 2 required for viability 1 (ARV1) is a putative lipid transporter of the endoplasmic reticulum that is conserved across eukaryotic species. The ARV1 protein contains a conserved N-terminal cytosolic zinc ribbon motif known as the ARV1 homology domain, followed by multiple transmembrane regions anchoring it in the ER. Deletion of ARV1 in yeast results in defective sterol trafficking, aberrant lipid synthesis, ER stress, membrane disorganization and hypersensitivity to fatty acids (FAs). We sought to investigate the role of Arv1 in mammalian lipid metabolism.Methods:Homologous recombination was used to disrupt the Arv1 gene in mice. Animals were examined for alterations in lipid and lipoprotein levels, body weight, body composition, glucose tolerance and energy expenditure.Results:Global loss of Arv1 significantly decreased total cholesterol and high-density lipoprotein cholesterol levels in the plasma. Arv1 knockout mice exhibited a dramatic lean phenotype, with major reductions in white adipose tissue (WAT) mass and body weight on a chow diet. This loss of WAT is accompanied by improved glucose tolerance, higher adiponectin levels, increased energy expenditure and greater rates of whole-body FA oxidation.Conclusions:This work identifies Arv1 as an important player in mammalian lipid metabolism and whole-body energy homeostasis.

Interventional Endoscopic Ultrasound

Endoscopic ultrasound (EUS) was developed as an adjunctive diagnostic modality to supplement cross-sectional imaging. EUS applications have expanded due to evolution in echoendoscope design, improved image resolution, and the development of fine needle aspiration (FNA) needles. This chapter will review current interventional EUS applications, including FNA, pseudocyst drainage, pancreatic necrosectomy, pancreaticobiliary access, celiac plexus interventions, cyst ablation, tumor injection, and vascular interventions.

Endoscopic Submucosal Dissection: Upper Gastrointestinal Tract

Endoscopic submucosal dissection (ESD) is an advanced endoscopic resection technique for the treatment of superficial cancers of the esophagus and stomach. Its advantages over traditional endoscopic mucosal resection techniques are higher curative resection rates and lower local recurrence. While ESD has become the standard of care in Japan for early gastric cancer, its initial adoption in the West was slow. However, as many of the barriers to Western adoption have now been overcome, we are seeing increasing interest and practice of this technique. ESD is indicated for early cancerous lesions of the esophagus and stomach with a negligible risk of lymph node metastasis. It has the potential for curative resection of these cancers while avoiding the morbidity and mortality associated with traditional surgery and allowing preservation of the native organ.