Sunil Sheth

A mitochondrial protein compendium elucidates complex I disease biology.

Mitochondria are complex organelles whose dysfunction underlies a broad spectrum of human diseases. Identifying all of the proteins resident in this organelle and understanding how they integrate into pathways represent major challenges in cell biology. Toward this goal, we performed mass spectrometry, GFP tagging, and machine learning to create a mitochondrial compendium of 1098 genes and their protein expression across 14 mouse tissues. We link poorly characterized proteins in this inventory to known mitochondrial pathways by virtue of shared evolutionary history. Using this approach, we predict 19 proteins to be important for the function of complex I (CI) of the electron transport chain. We validate a subset of these predictions using RNAi, including C8orf38, which we further show harbors an inherited mutation in a lethal, infantile CI deficiency. Our results have important implications for understanding CI function and pathogenesis and, more generally, illustrate how our compendium can serve as a foundation for systematic investigations of mitochondria.

Systematic identification of human mitochondrial disease genes through integrative genomics

The majority of inherited mitochondrial disorders are due to mutations not in the mitochondrial genome (mtDNA) but rather in the nuclear genes encoding proteins targeted to this organelle. Elucidation of the molecular basis for these disorders is limited because only half of the estimated 1,500 mitochondrial proteins have been identified. To systematically expand this catalog, we experimentally and computationally generated eight genome-scale data sets, each designed to provide clues as to mitochondrial localization: targeting sequence prediction, protein domain enrichment, presence of cis-regulatory motifs, yeast homology, ancestry, tandem-mass spectrometry, coexpression and transcriptional induction during mitochondrial biogenesis. Through an integrated analysis we expand the collection to 1,080 genes, which includes 368 novel predictions with a 10% estimated false prediction rate. By combining this expanded inventory with genetic intervals linked to disease, we have identified candidate genes for eight mitochondrial disorders, leading to the discovery of mutations in MPV17 that result in hepatic mtDNA depletion syndrome. The integrative approach promises to better define the role of mitochondria in both rare and common human diseases.

Nutrient-sensitized screening for drugs that shift energy metabolism from mitochondrial respiration to glycolysis

Most cells have the inherent capacity to shift their reliance on glycolysis relative to oxidative metabolism, and studies in model systems have shown that targeting such shifts may be useful in treating or preventing a variety of diseases ranging from cancer to ischemic injury. However, we currently have a limited number of mechanistically distinct classes of drugs that alter the relative activities of these two pathways. We screen for such compounds by scoring the ability of >3,500 small molecules to selectively impair growth and viability of human fibroblasts in media containing either galactose or glucose as the sole sugar source. We identify several clinically used drugs never linked to energy metabolism, including the antiemetic meclizine, which attenuates mitochondrial respiration through a mechanism distinct from that of canonical inhibitors. We further show that meclizine pretreatment confers cardioprotection and neuroprotection against ischemia-reperfusion injury in murine models. Nutrient-sensitized screening may provide a useful framework for understanding gene function and drug action within the context of energy metabolism.

Primary gallbladder cancer: recognition of risk factors and the role of prophylactic cholecystectomy

The objective of this article is to review the available literature on the epidemiology, predisposing factors, and conditions associated with primary gallbladder cancer, and to discuss the role of prophylactic cholecystectomy in high-risk patient populations. Gallbladder cancer is a highly malignant tumor with a poor 5-yr-survival rate. It is a tumor of the elderly and has striking genetic, racial, and geographic characteristics, with an extremely high prevalence in Native Americans and Chileans. Cholelithiasis is a well-established risk factor for gallbladder cancer and the risk seems to correlate with stone size. Polyps that are >l cm, single, sessile, and echopenic are associated with a higher risk of malignancy. Anomalous junction of pancreatico-biliary ducts (AJPBD), especially without choledochal cyst, and porcelain gallbladder are additional factors that predispose to gallbladder cancer. Lesser associations include chronic bacterial infections of the gallbladder, typhoid carrier state, certain occupational and environmental carcinogens, hormonal changes in women, and certain social, dietary, and familial factors. It is important to identify high-risk groups for gallbladder cancer because of the dismal nature of this tumor. In patients with porcelain gallbladder and anomalous junction of the pancreatic and biliary ducts, cholecystectomy is recommended provided that the patient is a good operative candidate. Patients with large solitary polyps or gallstones require close ultrasonic follow-up. With the advent of endoscopic ultrasound it is expected that early changes of malignancy in polyps will be reliably detected, and more patients will potentially be cured with a simple cholecystectomy.Through a MEDLINE/PAPERCHASE search we identified and reviewed articles regarding gallbladder cancer published in English-language journals between 1966 and 1999, using the key words biliary tract and gallbladder diseases, cancer, neoplasms, surgery, cholelithiasis, gallstones, cholecystitis, gallbladder polyps, risk factors, chemical industry, occupational diseases, typhoid, porcelain gallbladder, bacteremia, and precancerous conditions. We also used the bibliography of relevant articles to increase our search. A total of 122 publications were selected using the mentioned data source.

Analysis of Cystic Fibrosis Gener Product (CFTR) Function in Patients with Pancreas Divisum and Recurrent Acute Pancreatitis

BACKGROUND:The mechanism by which pancreas divisum may lead to recurrent episodes of acute pancreatitis in a subset of individuals is unknown. Abnormalities of the cystic fibrosis gene product (CFTR) have been implicated in the genesis of idiopathic chronic pancreatitis. The aim of this study was to determine if CFTR function is abnormal in patients with pancreas divisum and recurrent acute pancreatitis (PD/RAP).METHODS:A total of 69 healthy control subjects, 12 patients with PD/RAP, 16 obligate heterozygotes with a single CFTR mutation, and 95 patients with cystic fibrosis were enrolled. CFTR function was analyzed by nasal transepithelial potential difference testing in vivo. The outcomes of the PD/RAP patients following endoscopic and surgical treatments were concomitantly analyzed.FINDINGS:Direct measurement of CFTR function in nasal epithelium in response to isoproterenol demonstrated that the values for PD/RAP were intermediate between those observed for healthy controls and cystic fibrosis patients. The median value was 13 mV for PD/RAP subjects, which was statistically different from healthy controls (22 mV, p= 0.001) and cystic fibrosis pancreatic sufficient (−1 mV, p < 0.0001) and pancreatic insufficient (−3 mV, p < 0.0001) patients.INTERPRETATIONS:These results suggest a link between CFTR dysfunction and recurrent acute pancreatitis in patients with pancreas divisum and may explain why a subset of patients with pancreas divisum develops recurrent acute pancreatitis.

The Incidence and Clinical Spectrum of Refractory Celiac Disease in a North American Referral Center

OBJECTIVES:Refractory celiac disease (RCD) is one of the most serious causes of persistent symptoms in patients with celiac disease (CD). Published reports suggest that approximately half of patients in Europe are RCD type II, which carries a poor prognosis with a 5-year survival rate of ∼50% compared with ∼90% for RCD type I. However, disease patterns may be different in North America. The aim of this study was to explore the clinical spectrum of RCD in a North American population.METHODS:Medical records of patients with biopsy-proven CD presenting to our institution were reviewed for a diagnosis of RCD. Demographic data, clinical characteristics, and mortality were evaluated and compared with our general CD population.RESULTS:In all, 34 out of 844 (4.0%) CD patients had RCD. The cumulative incidence of RCD for patients diagnosed with CD at our center was 1.5%. Unintentional weight loss at diagnosis of RCD was found in 76.5% (n=26) compared with 16.7% (n=141) at diagnosis of CD (P<0.0001) and diarrhea at diagnosis of RCD was found in 79.4% (n=27) compared with 40.5% (342) at diagnosis of CD (P<0.0001). Five patients (14.7%) were diagnosed with RCD type II and of these, two died of enteropathy-associated lymphoma within 24 months of diagnosis of CD (observed mortality rate 5.9%).CONCLUSIONS:Although RCD is a serious condition with significant morbidity; the observed mortality rates are low in our population. This study suggests that RCD may be less severe in North American vs. European populations.

The Crohn's disease activity index (CDAI) is similarly elevated in patients with Crohn's disease and in patients with irritable bowel syndrome

While the Crohns disease activity index (CDAI) is the gold standard for defining clinical endpoints in Crohns disease (Crohns) clinical trials, its ability to distinguish symptoms due to inflammation from those that are non‐inflammatory has been questioned.

Time to endovascular reperfusion and degree of disability in acute stroke

Faster time from onset to recanalization (OTR) in acute ischemic stroke using endovascular therapy (ET) has been associated with better outcome. However, previous studies were based on less‐effective first‐generation devices, and analyzed only dichotomized disability outcomes, which may underestimate the full effect of treatment.

Celiac Crisis Is a Rare but Serious Complication of Celiac Disease in Adults

BACKGROUND & AIMS Celiac crisis is a life-threatening syndrome in which patients with celiac disease have profuse diarrhea and severe metabolic disturbances. Celiac crisis is rare among adults and not well documented. To improve awareness of this condition and to facilitate diagnosis, we reviewed cases of celiac crisis to identify presenting features, formulate diagnostic criteria, and develop treatment strategies. METHODS Cases of biopsy-proven celiac disease were reviewed. Celiac crisis was defined as acute onset or rapid progression of gastrointestinal symptoms that could be attributed to celiac disease and required hospitalization and/or parenteral nutrition, along with signs or symptoms of dehydration or malnutrition. RESULTS Twelve patients met preset criteria for celiac crisis; 11 developed celiac crisis before they were diagnosed with celiac disease. Eleven patients had increased titres of transglutaminase antibodies and 1 had immunoglobulin A deficiency. Results of biopsy analyses of duodenum samples from all patients were consistent with a Marsh 3 score (33% with total villous atrophy). Patients presented with severe dehydration, renal dysfunction, and electrolyte disturbances. All patients required hospitalization and intravenous fluids, 6 required corticosteroids, and 5 required parenteral nutrition. All patients eventually had a full response to a gluten-free diet. CONCLUSIONS Celiac crisis has a high morbidity and, although rarely described, occurs in adults and often has a clear precipitating factor. Patients who present with severe unexplained diarrhea and malabsorption should be tested for celiac disease; treatment with systemic steroids or oral budesonide should be considered. Nutritional support often is required in the short term but most patients ultimately respond to gluten avoidance.

Treatment of Helicobacter pylori infection with intra-gastric violet light phototherapy: A pilot clinical trial†

Helicobacter pylori infects the mucus layer of the human stomach and causes peptic ulcers and adenocarcinoma. We have previously shown that H. pylori accumulates photoactive porphyrins making the organism susceptible to inactivation by light, and that small spot endoscopic illumination with violet light reduced bacterial load in human stomachs. This study assessed the feasibility and safety of whole‐stomach intra‐gastric violet phototherapy for the treatment of H. pylori infection.