John C. Alverdy

The effect of parenteral nutrition on gastrointestinal immunity. The importance of enteral stimulation.

Secretory IgA (S-IgA), an immunoglobulin present in secretions, prevents the adherence of bacteria to mucosal cells and is the principle component of the gut mucosal defense system. The purpose of this study was to determine whether the route of nutrient administration affects S-IgA. Twenty-five female Fisher rats were randomized into three groups. Groups I and II were fed an isonitrogenous, isocaloric standard hyperalimentation solution, Group I intravenously and Group II via a gastrostomy. Group III (control) was fed rat chow and water ad lib. Since bile is one of the principle sources of S-IgA, animals had biliary T-tubes placed for sampling of bile every 4 days. At day 16, Group I animals were fed rat chow and water for an additional 8 days. S-IgA was measured by the ELISA immunoassay. Results indicated at day 16 that the S-IgA level in mg/ml of Group I was 1.1 +/- 0.2, while the S-IgA in Groups II and III was 2.2 +/- 0.6 and 2.2 +/- 0.26, respectively. Furthermore, the S-IgA level in Group I after 8 days of enteral feeding rose to 1.8 +/- 0.4. The difference in S-IgA levels between enterally and parenterally fed rats suggests that an important defense barrier is compromised during parenteral hyperalimentation. Rats fed the same nutrients by gastrostomy maintained S-IgA levels better than rats fed the same nutrients intravenously. The rapid return to normal levels after resumption of enteral feeding suggests that the intraluminal presence of foodstuffs is essential for maintenance of S-IgA.

Quality of Life and Psychosocial Adjustment in Patients after Roux-en-Y Gastric Report Bypass: A Brief Report

Background: While Roux-en-Y gastric bypass (RYGBP) appears to be the most effective procedure for weight loss in morbidly obese patients, objective outcome data regarding quality of life (QoL) and psychosocial status following surgery are lacking. Methods: The present study examined the effects of RYGBP in 32 morbidly obese subjects on a variety of outcome measures including QoL and psychosocial functioning. Assessments were conducted before surgery, 1 to 3 weeks post-surgery, and at 6- month follow-up. Results: In addition to weight loss, results show significant improvements in health-related QoL, depression, and self-esteem, as well as a significant reduction in eating pathology following surgery. Results also show that neither the presence of binge-eating disorder nor clinical depression predicted poorer outcome post-surgery. Conclusion: RYGBP results in a dramatic reduction in weight, and marked improvements in health-related QoL, depression, self-esteem, and eating pathology, including binge-eating in the short term. These findings need to be replicated in a larger cohort of patients and followed for a longer time before we can reach more definitive conclusions regarding the psychosocial outcome in RYGBP.

Duodenal switch provides superior weight loss in the super-obese (BMI ≥50kg/m2) compared with gastric bypass

Objectives:Although weight loss following Roux-en-Y gastric bypass is acceptable in patients with preoperative body mass index (BMI) between 35 and 50 kg/m2, results from several series demonstrate that failure rates approach 40% when BMI is ≥50 kg/m2. Here we report the first large single institution series directly comparing weight-loss outcomes in super-obese patients following biliopancreatic diversion with duodenal switch (DS) and Roux-en-Y Gastric Bypass (RYGB). Methods:All super-obese patients (BMI ≥50 kg/m2) undergoing standardized laparoscopic and open DS and RYGB between August 2002 and October 2005 were identified from a prospective database. Two-sample t tests were used to compare weight loss, decrease in BMI, and percentage of excess body weight loss (% EBWL) after surgery. χ2 analysis was used to determine the rate of successful weight loss, defined as achieving at least 50% loss of excess body weight. Results:A total of 350 super-obese patients underwent DS (n = 198) or RYGB (n = 152) with equal 30-day mortality (DS,1 of 198; RYGB, 0 of 152; P = not significant). The % EBWL at follow-up was greater for DS than RY (12 months, 64.1% vs. 55.9%; 18 months, 71. 9% vs. 62.8%; 24 months, 71.6% vs. 60.1%; 36 months, 68.9% vs. 54.9%; P < 0.05). Total weight loss and decrease in BMI were also statistically greater for the DS (data not shown). Importantly, the likelihood of successful weight loss (EBWL >50%) was significantly greater in patients following DS (12 months, 83.9% vs. 70.4%; 18 months, 90.3% vs. 75.9%; 36 months, 84.2% vs. 59.3%; P < 0.05). Conclusions:Direct comparison of DS to RYGB demonstrates superior weight loss outcomes for DS.

Diverting loop ileostomy and colonic lavage: an alternative to total abdominal colectomy for the treatment of severe, complicated Clostridium difficile associated disease.

Objective:To determine whether a minimally invasive, colon-preserving approach could serve as an alternative to total colectomy in the treatment of severe, complicated Clostridium difficile–associated disease (CDAD). Background:C. difficile is a significant cause of morbidity and mortality worldwide. Most cases will respond to antibiotic therapy, but 3% to 10% of patients progress to a severe, complicated, or “fulminant” state of life-threatening systemic toxicity. Although the advocated surgical treatment of total abdominal colectomy with end ileostomy improves survival in severe, complicated CDAD, outcomes remain poor with associated mortality rates ranging from 35% to 80%. Methods:All patients who were diagnosed with severe, complicated (“fulminant”) CDAD and were treated at the University of Pittsburgh Medical Center or VA Pittsburgh Healthcare System between June 2009 and January 2011 were treated with this novel approach. The surgical approach involved creation of a loop ileostomy, intraoperative colonic lavage with warmed polyethylene glycol 3350/electrolyte solution via the ileostomy and postoperative antegrade instillation of vancomycin flushes via the ileostomy. The primary end point for the study was resolution of CDAD. The matching number of patients treated with colectomy for CDAD preceding the initiation of this current treatment strategy was analyzed for historical comparison. Results:Forty-two patients were treated during this time period. There was no significant difference in age, sex, pharmacologic immunosuppression, and Acute Physiology and Chronic Health Evaluation-II scores between our current cohort and historical controls. The operation was accomplished laparoscopically in 35 patients (83%). This treatment strategy resulted in reduced mortality compared to our historical population (19% vs 50%; odds ratio, 0.24; P = 0.006). Preservation of the colon was achieved in 39 of 42 patients (93%). Conclusions:Loop ileostomy and colonic lavage are an alternative to colectomy in the treatment of severe, complicated CDAD resulting in reduced morbidity and preservation of the colon.

Influence of the critically ill state on host-pathogen interactions within the intestine : gut-derived sepsis redefined

Severe and prolonged states of catabolic stress have been shown to have profound effects on the intestinal tract microflora and intestinal function. Gut-derived sepsis is a term used to describe a state of systemic inflammation with organ dysfunction after severe catabolic stress hypothesized to be initiated and perpetuated by the intestinal tract microflora. Popular notions of the mechanism of this process have suggested that stress promotes the translocation of intestinal bacteria or their toxins into the systemic compartment resulting in the release of proinflammatory cytokines which participate in the systemic inflammatory response syndrome. This review is an attempt to redefine the mechanism of gut-derived sepsis by focusing on molecular events that result from host-pathogen interactions within the intestinal tract itself. This evidence-based review posits that gut-derived bacteremia, even with potent nosocomial pathogens, is an event of low proinflammatory potential and, itself, is an insufficient stimulus for the systemic inflammatory response and organ failure state typically seen after severe and prolonged catabolic stress. Mechanisms of this apparent paradox are discussed.

Redefining the Role of Intestinal Microbes in the Pathogenesis of Necrotizing Enterocolitis

Neonatal necrotizing enterocolitis (NEC) remains an important cause of morbidity and mortality among very low birth weight infants. It has long been suspected that intestinal microbes contribute to the pathogenesis of NEC, but the details of this relationship remain poorly understood. Recent advances in molecular biology and enteric microbiology have improved our ability to characterize intestinal microbes from infants with NEC and from healthy unaffected newborns. The lack of diversity within the neonatal intestine makes it possible to study gut microbial communities at a high level of resolution not currently possible in corresponding studies of the adult intestinal tract. Here, we summarize clinical and laboratory evidence that supports the hypothesis that NEC is a microbe-mediated disorder. In addition, we detail recent technologic advances that may be harnessed to perform high-throughput, comprehensive studies of the gut microbes of very low birth weight infants. Methods for characterizing microbial genotype are discussed, as are methods of identifying patterns of gene expression, protein expression, and metabolite production. Application of these technologies to biological samples from affected and unaffected newborns may lead to advances in the care of infants who are at risk for the unabated problem of NEC.

Gut-derived sepsis occurs when the right pathogen with the right virulence genes meets the right host: evidence for in vivo virulence expression in Pseudomonas aeruginosa.

ObjectiveTo define the putative role of the PA-I lectin/adhesin, a binding protein of Pseudomonas aeruginosa, on lethal gut-derived sepsis after surgical stress, and to determine if this protein is expressed in vivo in response to physical and chemical changes in the local microenvironment of the intestinal tract after surgical stress. Summary Background DataPrevious work from the authors’ laboratory has established that lethal gut-derived sepsis can be induced after the introduction of P. aeruginosa into the cecum of mice after a 30% hepatectomy. This effect does not occur when P. aeruginosa is introduced into the cecum of sham operated control mice. Previous experiments further established that the mechanism of this effect is due to the presence of the PA-I lectin/adhesin of P. aeruginosa, which induces a permeability defect to a lethal cytotoxin of P. aeruginosa, exotoxin A. MethodsThree strains of P. aeruginosa, one lacking functional PA-I, were tested in two complementary systems to assess virulence. Strains were tested for their ability to adhere to and alter the permeability of cultured human colon epithelial cells, and for their ability to induce mortality when injected into the cecum of mice after a 30% hepatectomy. To determine if PA-I is “in vivo expressed” when present in the cecal environment after hepatectomy, strains were retrieved from the cecum of sham-operated and hepatectomy-treated mice 24 and 48 hours after their introduction into the cecum and their PA-I expression was assessed. ResultsResults indicated that PA-I plays a putative role in lethal gut-derived sepsis in the mouse, because strains lacking functional PA-I had an attenuated effect on cultured human epithelial cells, and were nonlethal when injected into the cecum of mice after 30% surgical hepatectomy. Furthermore, surgical stress in the form of hepatectomy significantly altered the intestinal microenvironment, resulting in an increase in luminal norepinephrine associated with an increase in PA-I expression in retrieved strains of P. aeruginosa. Co-incubation of P. aeruginosa with norepinephrine increased PA-I expression in vitro, suggesting that norepinephrine plays a role in the observed response in vivo. ConclusionsLethal gut-derived sepsis may occur when intestinal pathogens express virulence determinants in response to environmental signals indicating host stress. In this regard, the PA-I lectin/adhesin of P. aeruginosa appears to be a specific example of in vivo virulence expression in colonizing pathogens in the intestinal tract in response to surgical stress.

Red death in Caenorhabditis elegans caused by Pseudomonas aeruginosa PAO1

During host injury, Pseudomonas aeruginosa can be cued to express a lethal phenotype within the intestinal tract reservoir—a hostile, nutrient scarce environment depleted of inorganic phosphate. Here we determined if phosphate depletion activates a lethal phenotype in P. aeruginosa during intestinal colonization. To test this, we allowed Caenorhabditis elegans to feed on lawns of P. aeruginosa PAO1 grown on high and low phosphate media. Phosphate depletion caused PAO1 to kill 60% of nematodes whereas no worms died on high phosphate media. Unexpectedly, intense redness was observed in digestive tubes of worms before death. Using a combination of transcriptome analyses, mutants, and reporter constructs, we identified 3 global virulence systems that were involved in the “red death” response of P. aeruginosa during phosphate depletion; they included phosphate signaling (PhoB), the MvfR–PQS pathway of quorum sensing, and the pyoverdin iron acquisition system. Activation of all 3 systems was required to form a red colored PQS+Fe3+ complex which conferred a lethal phenotype in this model. When pyoverdin production was inhibited in P. aeruginosa by providing excess iron, red death was attenuated in C. elegans and mortality was decreased in mice intestinally inoculated with P. aeruginosa. Introduction of the red colored PQS+Fe3+ complex into the digestive tube of C. elegans or mouse intestine caused mortality associated with epithelial disruption and apoptosis. In summary, red death in C. elegans reveals a triangulated response between PhoB, MvfR–PQS, and pyoverdin in response to phosphate depletion that activates a lethal phenotype in P. aeruginosa.

A differentiation-dependent splice variant of myosin light chain kinase, MLCK1, regulates epithelial tight junction permeability

Activation of Na+-nutrient cotransport leads to increased tight junction permeability in intestinal absorptive (villus) enterocytes. This regulation requires myosin II regulatory light chain (MLC) phosphorylation mediated by MLC kinase (MLCK). We examined the spatiotemporal segregation of MLCK isoform function and expression along the crypt-villus axis and found that long MLCK, which is expressed as two alternatively spliced isoforms, accounts for 97 ± 4% of MLC kinase activity in interphase intestinal epithelial cells. Expression of the MLCK1 isoform is limited to well differentiated enterocytes, both in vitro and in vivo, and this expression correlates closely with development of Na+-nutrient cotransport-dependent tight junction regulation. Consistent with this role, MLCK1 is localized to the perijunctional actomyosin ring. Furthermore, specific knockdown of MLCK1 using siRNA reduced tight junction permeability in monolayers with active Na+-glucose cotransport, confirming a functional role for MLCK1. These results demonstrate unique physiologically relevant patterns of expression and subcellular localization for long MLCK isoforms and show that MLCK1 is the isoform responsible for tight junction regulation in absorptive enterocytes.

The re-emerging role of the intestinal microflora in critical illness and inflammation: why the gut hypothesis of sepsis syndrome will not go away

Recent advances in the ability to genetically interrogate microbial communities within the intestinal tract of humans have revealed many striking findings. That there may be as many as 300 unculturable and unclassified microbes within the human intestinal tract opens the possibility that yet‐unidentified microbes may play a role in various human diseases [ 1 ]. Technologically, the regional and spatial aspects of intestinal microbial communities can now be better appreciated by emerging genetic and in vivo imaging systems using a bioinformatics approach [ 2 ]. Finally, in situ PCR of tissues and blood now allows the detection of microbes at concentrations that would otherwise remain undetected by culture alone [ 3 ]. In the aggregate, these studies have empowered clinicians to readdress the issue of how our microbial partners are affected by extreme states of physiologic stress and antibiotic use through the course of critical illness. The role of microbes in systemic inflammatory states, such as systemic inflammatory response syndrome, as well as in primary intestinal mucosal diseases, such as necrotizing enterocolitis, inflammatory bowel disease, and ischemia‐reperfusion injury, can now be more completely defined, and the microbial genes that mediate the immune activation during these disorders can be identified. The 2008 roadmap initiative at the National Institutes of Health to fully define the human microbiome is further testament to the power of this technology and the importance of understanding how intestinal microbes, their genes, and their gene products affect the course of human disease and inflammation.