Maneesh H. Singh

Evidence for Caspase Effects on Release of Cytochrome c and AIF in a Model of Ischemia in Cortical Neurons

Neuronal apoptosis following ischemia can be mediated by a caspase-dependent pathway, which involves the mitochondrial release of cytochrome c that initiates a cascade of caspase activation. In addition, there is a caspase-independent pathway, which is mediated by the release of apoptosis-inducing factor (AIF). Using caspase inhibitor gene therapy, we investigated the roles of caspases on the mitochondrial release of cyt c and the release of AIF. Specifically, we used herpes simplex virus-1 amplicon vectors to ectopically express a viral caspase inhibitor (crmA or p35) in mixed cortical cultures exposed to oxygen/glucose deprivation. Overexpression of either crmA or p35 (but not the caspase-3 inhibitor DEVD) inhibited the release of AIF; this suggests that there can be cross-talk between the caspase-dependent and the ostensibly caspase-independent pathway. In addition, both crmA overexpression and DEVD inhibited cyt c release, suggesting a positive feedback loop involving activated caspases stimulating cyt c release.

Effects of overexpression of antioxidants on the release of cytochrome c and apoptosis-inducing factor in the model of ischemia.

Apoptosis arises from neuronal damage following an ischemic insult. Apoptosis-inducing factor (AIF) is a protein released from mitochondria in response to pro-apoptotic signals which then translocates to the nucleus and triggers DNA fragmentation. In parallel with this, pro-apoptotic signals cause the release of cytochrome c from mitochondria, activating caspase-dependent apoptosis. During post-ischemic reperfusion, reactive oxygen species (ROS) are formed in excess in mitochondria and can play a role in initiating apoptosis. In cultures, ROS are formed during post oxygen glucose deprivation (OGD) normoxia/normoglycemia that is used as a model for ischemia. In this study, we delivered viral vectors to overexpress antioxidants (GPX, catalase, CuZnSOD, or MnSOD) in mixed cortical cultures, in order to investigate the effects of ROS-reduction on the release of cytochrome c and AIF. Overexpression of MnSOD, CuZnSOD, catalase or GPX all prevented AIF translocation from mitochondria to the nucleus. Potentially, this could reflect broadly non-specific protection due to reducing ROS load. Arguing against this, overexpression of the same antioxidants did not inhibit cytochrome c release. These findings suggest a specific interaction between ROS formation and the caspase-independent route of apoptosis.

Exercise capacity and paroxysmal atrial fibrillation in patients with hypertrophic cardiomyopathy

Background Atrial fibrillation (AF) is the most common arrhythmia among patients with hypertrophic cardiomyopathy (HCM). The relationship between paroxysmal AF and exercise capacity in this population is incompletely understood. Methods Patients with HCM underwent symptom-limited cardiopulmonary testing with expired gas analysis at Stanford Hospital between October 2006 and October 2012. Baseline demographics, medical histories and resting echocardiograms were obtained for all subjects. Diagnosis of AF was established by review of medical records and baseline ECG. Those with paroxysmal AF were in sinus rhythm at the time of cardiopulmonary testing with expired gas analysis. Exercise intolerance was defined as peak VO2<20 mL/kg/min. We used multivariate logistic regression to evaluate the association between exercise intolerance and paroxysmal AF. Results Among the 265 patients recruited, 55 had AF (28 paroxysmal and 27 permanent). Compared with those without AF, subjects with paroxysmal AF were older, more likely to use antiarrhythmic and anticoagulant medications, and had larger left atria. Patients with paroxysmal AF achieved lower peak VO2 (21.9±9.2 mL/kg/min vs 26.9±10.8 mL/kg/min, p=0.02) and were more likely to have exercise intolerance (61% vs 28%, p<0.001) compared with those without AF. After adjustment for age, sex and body mass index (BMI) exercise intolerance remained significantly associated with paroxysmal AF (OR 4.65, 95% CI 1.83 to 11.83, p=0.001). Conclusions Patients with HCM and paroxysmal AF demonstrate exercise intolerance despite being in sinus rhythm at the time of exercise testing.

Hypochlorhydria and achlorhydria are associated with false-positive secretin stimulation testing for Zollinger-Ellison syndrome.

Objectives Secretin stimulation testing (SST) is used to evaluate patients with hypergastrinemia in the diagnosis of Zollinger-Ellison syndrome. Case series have documented false-positive SST in patients with achlorhydria. This study reviews our experience with SST in hypochlorhydric and achlorhydric patients. Methods We examined 27 patients with hypochlorhydria or achlorhydria based on a predefined basal acid output (BAO) measurement of less than 5.0 mEq/h who also underwent SST for diagnosis of Zollinger-Ellison syndrome. We report the frequency of false-positive SST results in this setting. Results Three hundred thirty patients underwent gastric analysis of which 27 had BAO of less than 5.0 mEq/h and SST conducted. The mean (SD) fasting gastrin level was 247 (304) pg/mL, and the mean (SD) BAO measurement was 1.6 (1.8) mEq/h. Twenty patients were off, and 7 were on antisecretory therapy at time of testing. Four patients had false-positive SST results: 3 with gastric atrophy (BAO = 0 mEq/h) and 1 with drug-induced hypochlorhydria (BAO = 0.5 mEq/hr). These false-positive test results were confirmed by structural and functional imaging studies. Conclusions We have identified a 14.8% false-positive rate in SST in patients with hypochlorhydria or achlorhydria. Growing literature has identified severe consequences associated with discontinuing antisecretory treatment for testing; therefore, SST will require interpretation in the setting of gastric acid suppression and needs to be interpreted in this context.

Inadequate Utilization of Diagnostic Colonoscopy Following Abnormal FIT Results in an Integrated Safety-Net System

Objectives:The effectiveness of stool-based colorectal cancer (CRC) screening is contingent on colonoscopy completion in patients with an abnormal fecal immunochemical test (FIT). Understanding system and patient factors affecting follow-up of abnormal screening tests is essential to optimize care for high-risk cohorts.Methods:This retrospective cohort study was conducted in an integrated safety-net system comprised of 11 primary-care clinics and one Gastroenterology referral unit and included patients 50–75 years, with a positive FIT between April 2012 and February 2015.Results:Of the 2,238 patients identified, 1,245 (55.6%) completed their colonoscopy within 1-year of the positive FIT. The median time from positive FIT to colonoscopy was 184 days (interquartile range 140–232). Of the 13% of FIT positive patients not referred to gastroenterology, 49% lacked documentation addressing their abnormal result or counseling on the increased risk of CRC. Of the patients referred but who missed their appointments, 62% lacked documentation following up on the abnormal result in the absence of a completed colonoscopy. FIT positive patients never referred to gastroenterology or who missed their appointment after referrals were more likely to have comorbid conditions and documented illicit substance use compared with patients who completed a colonoscopy.Conclusions:Despite access to colonoscopy and a shared electronic health record system, colonoscopy completion after an abnormal FIT is inadequate within this safety-net system. Inadequate follow-up is in part explained by inappropriate screening, but there is an absence of clear documentation and systematic workflow within both primary care and GI specialty care addressing abnormal FIT results.

Yield of Colonoscopy After a Positive Result From a Fecal Immunochemical Test OC-Light

Background & Aims The fecal immunochemical test (FIT) is widely used in colorectal cancer (CRC) screening. The OC‐Light FIT is 1 of 2 FITs recommended for CRC screening by the Preventive Services Task Force guidelines. However, little is known about its ability to detect CRC in large average‐risk populations. Methods We performed a retrospective cohort study of patients (50–75 years old) in the San Francisco Health Network who were screened for CRC by OC‐Light FIT from August 2010 through June 2015. Patients with a positive result were referred for colonoscopy. We used electronic health records to identify participants with positive FIT results, and collected results from subsequent colonoscopies and pathology analyses. The FIT positive rate was calculated by dividing the number of positive FIT results by the total number of FIT tests completed. The primary outcome was the positive rate from OC‐Light FIT and yield of neoplasms at colonoscopy. Secondary outcomes were findings from first vs subsequent rounds of testing, and how these varied by sex and race. Results We collected result from 35,318 FITs, performed on 20,886 patients; 2930 patients (8.3%) had a positive result, and 1558 patients completed the follow‐up colonoscopy. A positive result from the FIT identified patients with CRC with a positive predictive value of 3.0%, and patients with advanced adenoma with a positive predictive value of 20.8%. The FIT positive rate was higher during the first round of testing (9.4%) compared to subsequent rounds (7.4%) (P < .01). The yield of CRC in patients with a positive result from the first round of the FIT was 3.7%, and decreased to 1.8% for subsequent rounds (P = .02). Conclusions In a retrospective analysis of patients in a diverse safety‐net population who underwent OC‐Light FIT for CRC screening, we found that approximately 3% of patients with a positive result from a FIT to have CRC and approximately 21% to have advanced adenoma.

Missed Opportunities in Colorectal Cancer Prevention in Patients With Inadequate Bowel Preparations

*Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington; Division of Public Health Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington; Division of Gastroenterology, University of Washington School of Medicine, Seattle, Washington; kDivision of Gastroenterology, University of California, San Francisco, San Francisco, California; Zuckerberg San Francisco General Hospital and Trauma Center, San Francisco, California; Division of General Internal Medicine, University of California, San Francisco, San Francisco, California; and **Center for Vulnerable Populations, University of California, San Francisco, San Francisco, California

Zollinger–Ellison Syndrome: Diagnosis and Management

Zollinger–Ellison syndrome (ZES) is a clinical entity originally described as the triad of gastric acid hypersecretion, peptic ulcer disease, and the presence of a non-beta islet cell tumor of the pancreas. The signs and symptoms of this syndrome are caused by the release of the gastric acid-driving hormone gastrin from a tumor of the gastrointestinal tract. The diagnosis of ZES requires the documentation of an elevated fasting serum gastrin level in the setting of gastric acid hypersecretion, most easily identified by a low gastric pH. The management of ZES falls into two categories: the control of gastric acid hypersecretion and its clinical manifestations through the use of proton-pump inhibitors and the management of the tumor itself. The treatment involves a multimodal approach that is comprised of surgery, radiation, chemotherapy, and, more recently, the use of targeted peptide therapy depending on the tumor stage.

645 Implementation of Fecal Immunochemical Testing Is Associated With Higher Screening Rates in a Safety-Net Population

Methods: A nurse delivered pre-procedure phone call for all scheduled procedures was instituted in October 2013 at a single tertiary care endoscopy center. In addition to standardized bowel prep instructions received in the mail, the nurse would call 2-7 days prior to the procedure to discuss the prep instructions in a scripted manner. The standard preparation used was bisacodyl 15mg and Miralax-Gatorade (238g of PEG-3350 in 64oz of Gatorade) in a non-split dose regimen. We performed a retrospective cohort study using the EndoWorks® database (Olympus America) and EPIC medical record (Epic Systems Corp., Verona, WI). All colonoscopy records from October 2012 to February 2013 (control, n = 1928) and October 2013 to February 2014 (intervention, n = 2088) were queried. Colonoscopy and pathology records were reviewed for patient demographics, indication, reported prep quality on the Aronchick scale, adenoma and sessile adenoma detection, size and location of polyps and incomplete procedures. In-patient (n = 115, 106) and diagnostic/therapeutic procedures (n = 702, 769) were excluded from the final analysis. Results: Patient demographics and procedure indication were similar amongst the control (n =1221) and intervention (n = 1309) groups on the basis of age (59.5 + 10.1 v. 59.8 + 9.8, p = .56), male gender (45.2% v. 48.7%, p = .08) and indication: screening (42.1% v. 41.1%, p = .55) and surveillance (21.5% v. 22%, p = .73). Of the colonoscopies performed for a screening indication, there was no difference among the control (n = 808) and intervention group (n = 854) in the rate of adequate preparation (78% v. 74.4%, p = .08), ADR (30.3% v. 28.9%, p = .53) including detection of right sided adenomas less than 5mm (7.1% v 7.6%, p = .66), sessile serrated adenoma detection rate (3.3% v. 4.5%, p = .24) or incomplete examination (6.2% v. 4.7%, p = .18). If colonoscopy performed for adenoma surveillance is added, there was no difference among the control (n = 1221) and intervention group (n = 1309) in adenoma detection rate (35.3% v. 35.4%, p = .997). Conclusion: A nurse delivered pre-procedure phone call to discuss bowel preparation prior to colonoscopy has no effect on adequacy of bowel preparation, adenoma detection or incomplete examinations.

PAROXYSMAL ATRIAL FIBRILLATION IS ASSOCIATED WITH EXERCISE INTOLERANCE AMONG INDIVIDUALS WITH HYPERTROPHIC CARDIOMYOPATHY

Atrial fibrillation (AF) is the most common arrhythmia among patients with hypertrophic cardiomyopathy (HCM). The relationship between AF and exercise capacity in this population is incompletely understood. We analyzed the association between AF and exercise capacity in a large HCM cohort. Patients